AC Owners Club Forum
AC Owners Club Forum => Mk IV, Superblower, CRS and other Continuation Cars Forum => Topic started by: Alan Faulkner-Stevens on July 29, 2006, 20:21:50
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For the many people who run 15inch wheels on their Cobras getting large rear tyres has been a serious problem due to a complete lack of suitable speed rated tyres. However I was at the Silverstone Historic Festival and passed the Avon tyre stand only to spot some large width section rubber. On discussion with the member of staff it transpires Avon have specifically manufactured some large width sized tyres for Cobra's and GT40's. These new tyres are road legal race spec. and are available now. I looked at some 295/50xVR15 which are an exact conversion for the 16inch tyres currently on the back of my CRS.
The Avon guy did not have any spec. sheets on the tyres as they were so new they had only been delivered to him the day before, but he promised to put a spec. sheet in the post to me. As soon as it arrives I'll post more information for interested parties.
regards Alan Faulkner-Stevens
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Hi Alan
Two questions:
1. From the size that you mention, I assume that these new tyres require a 15-inch rim, hence new rims for the CRS (or are they also doing a 16-inch variant?)
2. Do they have the equivalent (matching) front set in the same compound (225's on mine)?
Separately, I am interested to know how the compound compares to the Avon ZZ-1's I have on the car at the moment which are almost useless in the wet and not much better in the dry! Hopefully the spec sheets will help with this info.
Cheers, Bruce
PS: Perhaps Avon will give you a free set to 'road-test' on behalf of the club?!!
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Bruce, the new Avon tyres are designed for 15inch wheels. The 15inch wheels available are 7.5inches wide for the front and 9.5inches wide for the rear. Current 16inch wheels are 7 at the front and 8 at the rear. I parked next to a Lightweight at Silverstone last weekend and the larger wheels really charnge the appearance of the car. When I have the spec. sheet to hand I can make some suggestions for both a front and rear conversion for owners wanting to go from 16inch to 15inch. I'll keep you posted about this.
As to you ZZ1 problems, I have the same tyres on my own CRS and find the tyres satisfactory, just how hard are you pushing your car? My only comment about tyres is this, I worked with Avons directly when I was working for Aston Martin and I have always favoured their tyres out of choice, but it may be your tyres are just getting to old. If they are the original set and your car was produced in say 2000 they are at least 6 years old. They may have been manufactured up to a year before being fitted to the car making them even older. The older tyres get the harder they go, thus making grip harder to come by. Also what pressure are you running in them?
regards Alan
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Hello Allen,
Thanks for these complements of info. I just wonder how 295/50 VR 15 do compare in diameter and width to the original 255/50 VR 16 ?
As mentioned earlier on, MkIVs were originally equipped with 15" rims, later switched to 16", as on the CRSs. 17" Halibrands have also been available, though not AC factory original.
For 16" rimmed MkIVs and CRSs, the correct original tire spec is 225/50 VR 16 front and 255/50 VR 16 rear.
Michelin are offering again the Pilot Sport in the correct 225 and 255/50 ZR 16 size (Y rated), in their Collector Tyre program. My dealer here in Luxembourg has quoted a price of 192 € front and 355 € rear apiece & mounting & VAT. Delivery within a week. Sizes of the Pilot Sport are: (width / ext. diameter / circumference)
Front 225/50 ZR 16 : 242 mm / 642 mm / 1928 mm
Rear 255/50 ZR 16 : 276 mm / 672 mm / 2019 mm
PS for Bruce: 4-digit number usually in a “rectangle with rounded edges” indicates week and year manufactured (example 2403 means 24th week of 2003)
Best regards
Constant
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Hi Alan, Hi Constant
Alan, do you by chance have any photo's showing the difference between the two cars with different tyres? Personally I think the 15" rims give the car a more classic look, but I do like the aesthetic of the 16" rims. The wheel arches do look 'fuller' with the 15's though.
Constant, regarding your question of difference in tyre diameter, take a look at the following website:
http://www.rochfordtyres.co.uk/tyrecalc.asp
Per their calculator, the 255/50/16 has a diameter of 661.4mm (circumference of 2077.85mm) whereas the 295/50/15 has a slightly larger diameter of 676mm (circumference 2123.71mm)).
The website suggests that you should try keeping the tyre radius within 2.5% of the original. The 295 tyre is 2.21% bigger than 255 tyre, indicating that the tyre is within this range, making it a suitable alternative.
I do believe that the diameter will not be a problem when switching from 16" to 15" as there is plenty of space under the wheel arch. However, I wonder how the turing circle will be affected by the wider wheel rims (current 16" 7/8 front/rear rims versus the 15" 7.5/9.5). Alan, I look forward to reading your conversion advice.
Regarding my tyres.... I don't know how to benchmark how hard I'm pushing my car. It's normally pretty quick and I enjoy using the full range of power when suitable conditions / surroundings permit. One reference point was taking the CRS around the Nurburgring yast year. Despite two laps of the track as fast as I could (lots of tyre screeching and a few 'moments') the tyres were barely warm. I parked up, jumped out and put my hand on the tyre; the rubber didn't have any 'softness' to it and had the same temperature after being parked for 20 minutes. This is vastly different to the michelins on my motorbike which get nice and sticky after a bit of action.
Does anyone have any advice on suspension setup? Where could I go / who could I speak to about checking that my car is correctly set, as I sometimes feel that there is not sufficuent feedback through the suspension telling me what the suspension and tyres are doing.
Thanks for the tips on checking the tyres age; I'll check them tonight. I'll also check the tyre pressures, although from memory I am probably using about 2.5bar in front and rear (about 36psi).
Cheers
Bruce
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Dear Bruce, I am looking at the 295/50x15's to go directly on the back of my CRS instead of its 16inch wheels. I believe the rolling radii between the two tyres to be so similar as to not affect the speedo reading. When I have the spec. sheet I can find a suitable front conversion. I also think the tyres used on the front will be a similar width to the ones used on 16inch rims so I dont forsee a turning problem. These I already know about using another tyre manufacturer but I was hoping to have 4 matching tyres. As to 36psi...much to hard!!!! Try 28 all round and see how that feels. Alan
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Hi C9OBY,
I have a few photos of the wheel and tyre combo I took at the National Day and in Le Mans. Let me have an e-mail address and I can send them to you on Monday.
John.
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Hi Alan,
I took your advice and reduced the pressure in all tyres. What a difference - I'm not sure if I have exactly the right balance just yet as the tail felt a little 'squidgy'. Maybe too little pressure? Perhaps I'm just used to the rasor-sharp response I had from the tyres at the higher pressure.
The car also rides over rough surfaces/manhole covers with far more comfort than before. I took it around some remote roundabouts on Sunday far away from traffic and I definitely had more feel. I couldn't tell if grip was better, but at least I knew when it was about to let go!
Cheers, Bruce
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Bruce, please also check your rear damper adjustment. It may be the soft feeling on the rear of your car may be down to softer damping by the shock absorber. I'm fairly sure the damping settings are adjustable, so go up one setting and try this on the road again. Does your car have a rear anti-roll bar? If it does fine, but if not adding one will help rear end stability. Alan
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Hi Guys
I have the original tyres on my CRS (number 22), no rear anti-roll bar, and at 28lbs I think the tyres are still shockingly short of grip. I now know they were manufactured in 1999 (Thanks Alan) and I hope that the lack of grip is down to the fact that they're now too old. 3000 miles in 7 years? I'd hate to buy new tyres only to have to go out AND buy new tyres again and new wheels.
Personally I think I'll try to find some sticky rubber for the 16" wheel first before I do the new tyres and new wheels route.
It might be worth a mention that the adjustable rear shocks for the CRS are no longer manufactured so if they're weeping you have to get them re-built (always do both).
Mark-A
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Following on from Alan's investigative work (and numbers given to me by him) I have the following information on the Avon CR6ZZ tyres:
Call Avon racing department (in the UK) and speak to Brian on 01225 357 694. He gave me the following info:
The CR6ZZ tyres are effectively a road-legal race-compound tyre, promising much better grip in the dry and wet.
The 215/60/15's are each £147+VAT and the 275/55/15's are £188+VAT.
Avon are also doing a 295/55/15 tyre at £194+VAT, however it is suggested that the 275 rear is a better match for the 215 front, giving better balance. Some customers have been requesting a wider tyre for the front (235/60/15) in order to balance the wider 295 rear, but it is unlikely that this will be manufactured within the next 2 years.
They are based near Bath, but they will post them overnight to London for around £16.
Take a look at http://www.rochfordtyres.co.uk/tyrecalc.asp to see the difference in tyre diameters etc
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Thanks Bruce for the complement of info.
What will the MOT say about this, or alteratively, is there any chance to get an official statement (even earlyer in period) from AC about different tyre measures that are homologated for road use for the MkIV?
By the way I also have a set of 18" Halibrand rims that were developed by Uniclip some 3 or so years ago.
Regards
Constant
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quote:
Originally posted by Mark-Anthony
Hi Guys
I have the original tyres on my CRS (number 22), no rear anti-roll bar, and at 28lbs I think the tyres are still shockingly short of grip. I now know they were manufactured in 1999 (Thanks Alan) and I hope that the lack of grip is down to the fact that they're now too old. 3000 miles in 7 years? I'd hate to buy new tyres only to have to go out AND buy new tyres again and new wheels.
Personally I think I'll try to find some sticky rubber for the 16" wheel first before I do the new tyres and new wheels route.
It might be worth a mention that the adjustable rear shocks for the CRS are no longer manufactured so if they're weeping you have to get them re-built (always do both).
Mark-A
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Originally posted by Mark-Anthony
Hi Guys
I have the original tyres on my CRS (number 22), no rear anti-roll bar, and at 28lbs I think the tyres are still shockingly short of grip. I now know they were manufactured in 1999 (Thanks Alan) and I hope that the lack of grip is down to the fact that they're now too old. 3000 miles in 7 years? I'd hate to buy new tyres only to have to go out AND buy new tyres again and new wheels.
Personally I think I'll try to find some sticky rubber for the 16" wheel first before I do the new tyres and new wheels route.
It might be worth a mention that the adjustable rear shocks for the CRS are no longer manufactured so if they're weeping you have to get them re-built (always do both).
Mark
I had an issue here in the states finding rubber for the f & R of the 16's. While they are not optimal for racing i find the Dunlop SP8000's in 255 & 225 50x16 very nice, but then I'm comparing them to the 20 year old originals that came on the car
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Hi Jbottini
Many thanks for the info on tyres. I'll checjk them out and let all know.
Mark-Anthony
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For those interested, I have now fitted my CRS with new 15-inch rims and a brand new set of nice sticky Avon CR6ZZ tyres (215/60/15' and 275/55/15).
The ride is far more supple with slightly higher ground clearance. The tyres have fantastic grip, even when cold. I'm looking forward to putting some distance on them this weekend - updates to follow.
Photo's available on request.
Bruce
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Hi Bruce,
Yes to photos please e-mail them to John@moonlightmedia.co.uk
I look forward to your updates.
Cheers - John.
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Hi Bruce
Love to see some photos (prefer to see the car!)
can you e-mail them to my addr
mark-anthony.conti@simonefix.com
please?
M-AS
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Guys, I have received Bruces pictures of his CRS converted to 15inch rims and the car looks fantastic. It does for me give the car a very sixties look and does nothing but enhance its appearence. I'm so impressed I have ordered a set for my CRS!! I'm also converting to quick-lift bars over the winter, best wishes to all
Alan Faulkner-Stevens
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Hi guys
Feedback on the new Avon CR6ZZ tyres:
Following a cracking drive down to the AC Sprint at Goodwood this weekend with sunny skies and dry roads, I managed to get together some early view on these fantastic new tyres.
First, the ride is now noticeably smoother. The extra rubber on the 15-inch rims soaks up some of the road surface and softens the bumps, but without loosing 'feel' of the road. Interstingly, I now believe that the feel is better, as the tyres are far less skittish and track much better (combination of the rubber compound and 16-to-15inch conversion).
Road holding:
The tyres are very grippy, even when cold. I've already mentioned that they have a nice tacky feel and this gets noticeably stickier as the tyres warm up. However, I am well aware that the softer compound will have shorter life than my old tyres. Considering the relatively low mileage spent in the car each year, I do feel that this is a satisfactory compromise.
Cornering is a pleasure! The car hold the road like never before, but again with far more feel and composure. Before the car felt a little twitchy on the bends and I was never 100% sure where the limits of the car were. The tyres retain far more contact with the road, never sliding or 'hopping' across uneven surfaces as they did on the old rubber. Twisting through the forests and passes near Goodwood was a pleasure with the tyres giving me a new level of confidence in the car.
Braking:
For obvious reasons, these tyres brake far better. These cars have great brakes and on the old tyres the wheels sometimes locked up under firm braking when they should not have done so. As you learn a car, you quickly know where it's limits are, making compromises/allowances as you go. With these tyres, I no longer have that 'cold tyre' fear when I leave home. They stop the car quickly with no twitches. Before, different wheels would grip/slow at different times depending on the road surface, unsettling the car and making braking a very involving process. Now, the car slows evenly with composure, the tyres biting into the road surface, leaving me free to focus my attentions on the other things around the car.
High speed:
On fast a/b roads, the car is noticeably steadier. I put this down to both the bigger sidewall giving more consistant road contact and the tyres being that bit softer. The steering is a little lighter (also due to the slightly narrower tread section of 215 vs the original 225) but responds quickly to direction change.
Honestly, I cannot say enough about these tyres. The old tyres are sitting in my garage on the old 16-inch rims. I'll save them for a track day one day but would never sell them on as I would not trust them on another road car. Anyone who wants to come for a ride and see the difference for themselves is welcome.
My advice - get safe and trade up ! It's been well worth the £2,825 investment.
Bruce
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before
(http://i139.photobucket.com/albums/q311/c9oby/3frontleftbefore.jpg)
after
(http://i139.photobucket.com/albums/q311/c9oby/4frontleftafter.jpg)
(http://s139.photobucket.com/albums/q311/c9oby/IMG_6696.jpg)
(http://i139.photobucket.com/albums/q311/c9oby/IMG_6704.jpg)
(http://i139.photobucket.com/albums/q311/c9oby/IMG_6744edited2.jpg)
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Great looking car and while I'm running 16's; I must admit the 15's are a nicer look. Seem to fill the wheel arches better. Do you know mfgr and pn of the rear view mirrors? Jim
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Wow, that looks really nice, who are the rims made by???
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jbottini
The rear view mirrors look like the ones found in:
http://www.europaspares.com
Look in the onlineshop and then exterior mirrors,SVAMIRL L/H or R/H for £76.00 Daylight robbery just because they are SVA approved otherwise they would be about £20-25
Try: https://secure.visav.co.uk/avshop/products.asp?getcats=true&page=8&cat=16&scat=79&sscat=&sword=
Jim H
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Thanks, I'll look into them. I'm using windshield post mounted "raydots' and can't seem to get them right. jim
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Hi Jim,
If its any help to you I have been supplied with the following mirror from AC Cars in Malta, as part of my build package. AC Cars part number refernce being 2359-025
Its made by;
TEX Classic
Pt. No. M68890
and is described as; Convex anti dazzle polished
I will send you a picture of mine. It looks to be the same as the one in the pictures above. Lovely car by the way Mr C90BY!!
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quote:
Originally posted by jbottini
Thanks, I'll look into them. I'm using windshield post mounted "raydots' and can't seem to get them right. jim
FYI Jim, It's "Raydyot" [:D] I just LOVE findind other peoples errors!!!! (As I NEVER make any myself!)
Rick
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Can I ask .. .do they make wider wheels in the 16" variety .... 16 x 8" on the front of my Pantera and maybe 16 x 13" on the rear or some thing close to that would be real nice.
Who made the 16" rims ???
Ron
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The 16" rims were made by (brain fart, it will come to me) and were done out of permanent molds rather than sand cast. Brian Angliss told me how much they cost...rather a large sum at the time as he had only sold a few cars, it was a "leap of faith" he made.
I will post as the answer comes to me or someone will look at their MK IV/Superblower/CRS and beat me to it.
And no, they only are made in the original Autokraft sizes.
Rick
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I'll look tomorrow. Hey Rick, can you help the guy I emailed you about the brakes..superarnie? Rayddots smayydots too Jim
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Wow. I have to say the 15" conversion looks to have it ALL over the 16`s.
Everything. Tread pattern, proportions, Those beautiful Halibrands (are they from Gerry Hawkridge?)....PLUS the driveability you mention, what a transformation.
It appears that the 15" is about an inch taller than the 16", is that enough to affect your speedo reading? (or economy....hehehe?)
Nik.
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quote:
Originally posted by nikbj68
Wow. I have to say the 15" conversion looks to have it ALL over the 16`s.
Everything. Tread pattern, proportions, Those beautiful Halibrands (are they from Gerry Hawkridge?)....PLUS the driveability you mention, what a transformation.
It appears that the 15" is about an inch taller than the 16", is that enough to affect your speedo reading? (or economy....hehehe?)
Nik.
Hi there
Yes, I got the rims from Gerry Hawkridge. I'm not sure where he gets them from, but I'll look for the box/paperwork that they came in for any clues etc. The photo is slightly misleading, as the difference in diameter is actually less than an inch. I suspect that it does affect the speedo, although I don't know by how much. I'm waiting for the chance to pace someone else in another car and compare readings.
Cheers
Bruce
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quote:
Originally posted by C9OBY
quote:
Originally posted by nikbj68
...Those beautiful Halibrands (are they from Gerry Hawkridge?)....
Nik.
Hi there
Yes, I got the rims from Gerry Hawkridge. I'm not sure where he gets them from, but I'll look for the box/paperwork that they came in for any clues etc. ...Cheers
Bruce
I believe Gerry Hawkridge manufactures them himself, along with the original spec Lancia Stratos wheels that he sells, primarily to go on his Replicas, but they are fitted to some original cars I`m told.
Just looking at your pics again, No contest. I think the 15" should be compulsory [:D] [8D][8D]
[edit] Check here: http://www.hawkcars.co.uk/parts/index.html For details of Hawkridge wheels, and mirror mounts too!
(http://www.hawkcars.co.uk/parts/hawkwheelrange.jpg)
(http://www.hawkcars.co.uk/parts/427scmirror.jpg)
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Hi all,
The 16 inch Halibrand style wheels found on the CRS and Superblower cars are/were made by a company in the UK called 'Compomotive Motorsport'
I do have the parts numbers for the front and rear but will have to go and take them off the boxes supplied to me- if anyone needs them please let me know.
Regards
Gary
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Superarnie, you are correct, I just at the rear of a spare rear wheel and my spare tire & wheel. Hope to have pn's off my calipers for you today. i assume they are same rim widths as the cars' frome and body dimensions are relatively equal. The MKIV's SB's & I believe the CRS's have Frua rear uprights to pick up rear track (4")and different front uprights to expand front as well over the MK III. Jim
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Hello Bruce,
The tyres look good.
Where did you secure the braces for attaching the safety harness to the roll hoop?
Regards
Constant
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quote:
Originally posted by MkIV Lux
Hello Bruce,
The tyres look good.
Where did you secure the braces for attaching the safety harness to the roll hoop?
Regards
Constant
Hi Constant,
I hope you're well and not allowing the Luxembourg winter to stop you getting out & about in the cobra!
I got the brackets from Hawk cars too (Gerry Hawkridge). He gets them made by Kirkham - milled from aluminium block to the exact diameter of the CRS roll-hoop (I suspect that the roll-hoop on yours is a larger diameter. They were made to his specification, so I'm sure he cound get a set made to fit yours exactly if you asked him).
Unfortunately he has run out of stock and is waiting for a new batch. I bought his last two for circa £40 each about a month ago so he may well have more in by now. However, when he ordered more, they quoted him about £80 each. When we last spoke, he was in the process of negotiating a lower price. I also need another set so that I can do the passengers side too.
Cheers
Bruce
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Hi Bruce,
Thanks for the info.
If you think it helps to place a bigger order, maybe you can ask for a pair for me at the same time, for the Mk IV hoop.
Just let me know.
Kind regards
Constant
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If of any interest, I have noticed there is a full set of Halibrand wheels currently on Ebaymotors (Auction number 110067124128). The current price is $800.00 which at todays exchange rate works out at about £400.00. They look to be in superb condition and I think they are supplied with the spinners. Shipping of them to the UK may be around another $200-300. They come complete with Goodyear Eagle tyres. You could make quite a saving!!
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Just received thie following from Gerry Hawkridge:
HAWK CARS LTD. ARE DELIGHTED TO ANNOUNCE THE PRODUCTION OF YET ANOTHER
NEW WHEEL .
AS WELL AS PRODUCING THE FABULOUS LANCIA STRATOS "COFFIN SPOKE"
WHEEL, AND THE 7.5 x 15 and 9.3 x 15 Mk 3 HALIBRAND STYLE WHEELS FOR THE
427 COBRAS -
WE NOW OFFER A NEW WHEEL TO SUIT THE 289 FIA COBRAS AND DAYTONAS.
THIS WHEEL, STYLED AS THE HALIBRAND FIA WHEEL, IS PRODUCED IN 6.5 x 15"
AND 8.5 x 15" SIZES, IT HAS 6 PEG DRIVE, (SPLINE DRIVE FITMENT WILL ALSO
BE AVAILABLE SHORTLY) AND IS DIMENSIONALLY THE SAME AS ORIGINALS. IT IS
GRAVITY DIE CAST IN LM25 ,AND THE QUALITY AND ACCURACY IS SUPERB.
FOR MORE INFORMATION,PLEASE DO NOT HESITATE TO CONTACT GERRY
HAWKRIDGE AT HAWK CARS, 0044(0)1892750341 or e-mail gerry@hawkcars.co.uk (http://"gerry@hawkcars.co.uk")
Best regards Gerry Hawkridge.