Leadership Team SLR No.77 Posted June 18, 2007 Leadership Team Share Posted June 18, 2007 Ok, need some advice, I've hit a bit of a handling dilemma ....... My last 7, after many years of ownership had become set up pretty nicely to give neutral balanced handling (minimal amount of understear being controllable on or off throttle) - a combination of widetrack & standard springs allied with 6" front/7" rear wheels, 185 & 215 Yoko 32Rs, red ARB and adjustable rear, 15mm chassis rake, 65mm at the sump, 0º tracking at the front. There you go, a complete car setup in one sentence 😬 Having swapped to an SLR which was purchased shod with 6" front/7" rear wheels with 185/60 Yoko 539s, I've swapped the wheels/tyres for the more common SLR setup of 6½" front 8½" rears, 2 sets, one shod with 175 & 205 CR500s, the other with 195 & 245 ACB-10s. The car was originally factory supplied with ACB-10s therefore I'm assuming the DeDion ears are for the crossply setup. the only other changed item is the front ARB to a red one (the old one was a big beast!). Having done around 500 sensible speed road miles on the CR500s, I went to Anglesey on Friday 😬. Suffice to say my first impression of CR500s compared to Yokohamas is that they're bl%%dy aweful!!! But of course it could be the setup of the new car! The understeer is horrendous, to the point where the front wheels are squeeling badly at higher cornering speeds, this being on a drying track. The faster I pushed, even using a very neutral throttle through the entire corner I'm still suffering the front end push and squeel! The track dried enough over lunch to swap to the ACB-10s - with the obvious concern that if the setup is understeering with 205 rears it's going to die a death with 245s Not so - it was totally neutral with amazing turn-in and the ability to balance the rear completely on the throttle. I'm not experienced with 7s on Avon tyres, I've always stuck with Yokohamas, and I'd heard that ACB-10s were fantastic in dry conditions, but to show such a difference in balance was a major surprise! The dilemma now is that I want to use CR500s for normal road use and wet tracks, and the ACB-10s purely for dry tracks, but something needs to change in the setup. And for once I really haven't a clue where to start!!!!! I'm even considering ditching the CR500s in favour of Yoko 48s but it seems a bit drastic at this stage! Any suggestions where to start? Stu. www.superse7ens.co.uk..........the rebuild 😬 Edited by - sforshaw on 18 Jun 2007 21:48:27 Link to comment Share on other sites More sharing options...
Paul McKenzie Posted June 19, 2007 Share Posted June 19, 2007 Stu, Do you have a typical ACB10 setup with next to no camber on the front? If so this will not help the front end grip of the CR500's which like lots of negative camber, in some cases all you can get on the top link. Paul Link to comment Share on other sites More sharing options...
Petrolhead Posted June 19, 2007 Share Posted June 19, 2007 Hmmmm My understanding after reading many posts on BC from people wanting to run XPly and Radial tyres on the same car is that CR500 as supposed to be fine with minimal camber NE7Club Web Site R5 no 65 😬 Trackday 2nd April Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 19, 2007 Author Leadership Team Share Posted June 19, 2007 I haven't measured the camber at the front but there certainly isn't much if any at all. I know the DeDion ears are normally changed for radials but my understanding is that radial tyres are more tolerant of a cross-ply setting than the other way around? Nothing looks amiss visually therefore I'm stumped where to start with such a definate difficulty on CR500s - maybe I need to methodically measure everything accurately as a starting point. car drives great at road speeds but very noticeable problem on track. Although the car was running 539s, I don't think it has been specifically setup for these. The previous owner had reduced the rear wheel size from 8" to 7" stating the originals were too wide and fitted 185s all round. This is with 244 bhp on tap! I'm suspiscious the car is setup for ACB-10s and will need a tyre change to possibly Yokohama if they are more setting tolerant than the CR500s? I still intend to have a road/wet-track set, and the ACB-10s for dry track use. I don't like eating normal multi-purpose road tyres on a dry track! Stu. www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
Rob Walker Posted June 19, 2007 Share Posted June 19, 2007 I don`t think that you can have the best of both worlds. I run crossply slicks on track with virtually no neg camber and a fairly stiff set up which works well but on the road or wet track I run yoko 48`s and they do not perform well I think mainly because of the lack of negative camber. Not sure if there is a solution . Link to comment Share on other sites More sharing options...
I reply to every thread Posted June 19, 2007 Share Posted June 19, 2007 I have the same problem on track - CR500's are fine on the road but I found them diabolical on track compared to 32R's. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 19, 2007 Author Leadership Team Share Posted June 19, 2007 I'm beginning to think I should leave everything alone until the CR500s are dead, then swap back to Yokos! I guess it has to be 48s now, assuming the 32s are still out of production? Stu. www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
Mark Piper Posted June 19, 2007 Share Posted June 19, 2007 The Cr500s and ACB10s ran on the same (CR500) ears with no problem on my HPC. I ran my CR500s at Cadwell recently on the wet Club trackday and they performed well (R500). I have run CR500s them in the dry at Brands and they did overheat at Clearways (SLR) - where I always seem to understeer regardless of what tyres I use . Hyperion run their front CR500s the "wrong way round" - I understand this reduces understeer. In general, I'd expect 32s and 48s to be bettter than CR500s on track - they are far more dry road biased after all 🤔 ❗ Link to comment Share on other sites More sharing options...
DSL Posted June 19, 2007 Share Posted June 19, 2007 Your problem mainly stem from the lack of negative camber on the front CR500's, when people say they work ok on ACB settings its either they dont drive the car anything like hard enough or they must just mean it does'nt do anything nasty on those settings. But it sure as hell does not grip anything like it should with out the negative camber being increased to more normal levels Link to comment Share on other sites More sharing options...
Graeme Smith Posted June 19, 2007 Share Posted June 19, 2007 Hyperion run their front CR500s the "wrong way round" - I understand this reduces understeer. Don't think so - it's to prevent them delaminating Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 19, 2007 Author Leadership Team Share Posted June 19, 2007 Ok, I've measured the camber at the front wheels - it's approx 1.3º negative. Is this anywhere near what's needed for CR500s? Stu. www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
6speedmanual Posted June 19, 2007 Share Posted June 19, 2007 Graham Smith/Mark Piper I understood that CR500 gave greater braking grip in DRY when running in reverse rotation. Never heard any reference to understeer, but it could be so. 🤔Who knows 🤔 There is a lot of anecdotal stuff about tyres which goes round like chinese whispers. Stu CR500 front suspension setting up to 2.25 deg neg camber for track use. my penn'orth Does anyone involved in Caterham racing have any proper test data comparing different tyres' performance - lap times/grip/wear/issues when track temp hot or cold 🤔 Could make interesting reading...... 6SpeedManual *tongue*There's no such thing as too much BHP per Ton 😬 Link to comment Share on other sites More sharing options...
Trevor Newman Posted June 19, 2007 Share Posted June 19, 2007 I am with Graeme on this one The tyre is designed to take accelerative forces from the powered wheels, they dont cope too well with the braking forces a caterham can generate. Link to comment Share on other sites More sharing options...
Graeme Smith Posted June 19, 2007 Share Posted June 19, 2007 Does anyone involved in Caterham racing have any proper test data comparing different tyres' performance - lap times/grip/wear/issues when track temp hot or cold The Super and Mega Grad lap records are here - some of them have the old lap record on CR500, as opposed to the A048Rs they run now - the 48Rs seem to be 2 or 3 seconds a lap quicker at most circuits... CR500s are faster in the wet though. Link to comment Share on other sites More sharing options...
Trevor Newman Posted June 19, 2007 Share Posted June 19, 2007 Owjay and I went up against the Roasdsport spec no headlights and aero screens shod with the current CR500, in an equivalent power but with windscreens headlights and 48's and still managed to lead the pack for several laps. In the wet the CR500s should be better but running with 48s on the wrong way round never slowed me down 😬 Link to comment Share on other sites More sharing options...
Paul McKenzie Posted June 19, 2007 Share Posted June 19, 2007 Stu, My mate Dave's SLR on CR500's has max. neg. camber (no visible threads on upper link) which must be 6 degs. total and it turns in like a beast ..this is where your problem lies. Paul Link to comment Share on other sites More sharing options...
Slipper man Posted June 20, 2007 Share Posted June 20, 2007 Ditch the CR500's. My R500 was exactly the same on those tyres - if you were really brutal on turn in they went very well, but it was no fun. A swap to 48R's fixed it. I was not impressed with CR500's. And a new set of rears was more expensive than a complete set of 48R's! Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 20, 2007 Author Leadership Team Share Posted June 20, 2007 I seem to be falling in either of 2 directions ..... 1. Set the car up properly for CR500s and use them on track also (maybe run two sets keeping a more worn set for dry track)? 2. Swap the CR500s for 48s to use on the road/damp/wet tracks, and keep the ACB-10s for dry track use? This would prevent the punishment to the 48s that I used to experience on track with 32s. 3. Maybe even use 48s for road & track, and put a set of proper wets on the spare set of wheels? Whichever option, there appears to be little possibility that a compromised setting can work for both ACB-10s and CR500s. Added to that having experienced ACB-10s on a dry track, it's akin to having opened Pandora's box Stu. www.superse7ens.co.uk..........the rebuild 😬 Edited by - sforshaw on 20 Jun 2007 13:04:05 Link to comment Share on other sites More sharing options...
Mark Piper Posted June 20, 2007 Share Posted June 20, 2007 it's akin to having opened Pandora's box You wanna try slicks Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 20, 2007 Author Leadership Team Share Posted June 20, 2007 No no no no no no no no no no no no no no.......... repeat after me ..... NO! www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
Casbar Posted June 20, 2007 Share Posted June 20, 2007 Use CR500's on the road and for wet track use, then get a set of used Radial slicks for dry track use. No need to swap de-dion ears, so setup stays the same. I don't do a lot of road miles and run the same size CR500's all around that way the rolling circum is the same as 6" slicks on the front and 7" rears. Which works fine with R300 power levels Link to comment Share on other sites More sharing options...
elie boone Posted June 20, 2007 Share Posted June 20, 2007 Maybe the wider tyres give a different rake of the chassis, the rear sits a little bit higher with this combo so it will give less understeer. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 20, 2007 Author Leadership Team Share Posted June 20, 2007 Anyone remember which DeDion ears are used for crossplies, radials? www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted June 20, 2007 Area Representative Share Posted June 20, 2007 Ears:- Radials = 1.5° (but most that I've measured are more like 1.75°) Crossplies = 0.5° (but maybe 0.25°) Link to comment Share on other sites More sharing options...
Ian R Posted May 26, 2008 Share Posted May 26, 2008 Stu Hi, just came across this thread, just curious as to what you did in the end as I have a similar dilemma to you?! Cheers Ian Link to comment Share on other sites More sharing options...
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