frankyknuckles Posted June 21, 2004 Share Posted June 21, 2004 Having changed wheels and tyres from 15x6.5" (195/45) CR500's all round to 13x6 (185/60) front and 13x8 (205/60) rear with YokoAO48R's, I have a few questions about the handling characteristics. Before the change my car was flat floored by CC with their 'standard setup' which I presume has not changed over the last 4 months (but the tracking is very very slightly out). With the 15" wheel tyre combo, I had no understeer and felt very confident with the amount of grip I had. After the change, I have noticed that the steering feels alot lighter (which is a good thing), but after my first real blat with at the weekend, I was experiencing what I think was slight understeer. The car seemed to get light at the front during cornering and when deliberately pushing round a roundabout, the front would wash out a bit (understeer) before biting and turning. I also has a few rear tyre squeals round a few corners that I have never had before with the CR500's. I am running all tyres at 18psi (cold). The first instance of understear I noticed happened when the tyres were cold (I had only driven half a mile), but the second instance, the tyres should have been warm, I had driven about 10 miles. All of this occured on Sunday morning which was quite cold and windy but with dry roads. In all situations, I am feeling that the car is very light at the front and although not always understeering, it feels very 'drifty' with the 13's and Yokos. 1. Is this normal? I appreciate that there is 10mm less front tyre width, but should this be causing this kind of difference? My car really does feel very different and I am less confident of the front end grip. 2. Tyre pressure is probably important, is 18psi correct? some people have suggested maybe 14 or 15psi (cold) will produce more grip and produce a better more even wear rate. 3. Do Yoko's take time to warm up and do they need a higher operating temperature than CR500's? 4. Is it beacuse I am pushing it a bit more and starting to find the limit on a more regular basis? I am starting to drive the car alot quicker, but not to speeds where I should be seeing the limit of the tyres(?) 5. With changing the wheels and tyres I have effectively lowered the front end by about 5mm so there is more rake than before, but this should cause oversteer and not understeer? 6. Maybe I should go and see Gary at Freestyle who appears to be the guru when it comes to sorting out the balance of 7's. Maybe the front ARB is too stiff for road use with the Yoko's? Thanks for any thoughts you might have on this. Dave www.R300.net Link to comment Share on other sites More sharing options...
Nick Woods Posted June 21, 2004 Share Posted June 21, 2004 My first though is how many miles have you done on the new tyres ? A lot of them have some sort of mould release compound on that takes a couple of hundred miles to scrub off completely Nick Red and Black 1.6K supersport visit Carrotland.co.uk Link to comment Share on other sites More sharing options...
Jason Plato Posted June 21, 2004 Share Posted June 21, 2004 I was running 32R's , this year I have changed to 48R's . I dont rate the 48r's in medium compound ( the only compound available at present ) , when sprinting my car understeers more with the 48R's compared to soft or super soft 32R's . On trackdays , the 48R's still "go off" after 6 hard laps and take longer to heat up . Whatever the marketting blurb says , I dont feel these are a step forward in dry conditions . Dave Lotus 7 Club Speed Champion 2003 South Wales Area Organiser C7 TOP Link to comment Share on other sites More sharing options...
wag Posted June 21, 2004 Share Posted June 21, 2004 Blast, ive just bought 4. Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted June 21, 2004 Support Team Share Posted June 21, 2004 When I switched from A021R to A048R, I noticed the car was much more of a handful on the road and not as grippy. I dropped the pressures by 1-2 psi and things improved hugely. I think that the 48s are very sensitive to pressure - maybe the sidewalls are a bit stiffer than 21s (and CR500s). Try reducing the pressure in the fronts to 17 or maybe even 16 psi. Nick's comment is also relevant - the mould release compund takes a couple of hundred miles to scrub off (or a few hard laps on track I guess 😬) Yellow SL #32 Link to comment Share on other sites More sharing options...
frankyknuckles Posted June 21, 2004 Author Share Posted June 21, 2004 Thanks, I will try a different pressure, should I drop the pressure in all 4 tyres? I have done about 150 miles tops with new tyres. www.R300.net Link to comment Share on other sites More sharing options...
Jason Plato Posted June 21, 2004 Share Posted June 21, 2004 Try 16 front , 19rear . Dave Link to comment Share on other sites More sharing options...
dino ferrana Posted June 21, 2004 Share Posted June 21, 2004 CR500s are a fair bit lighter than the A048Rs which afterall are designed for a heavier car than a Caterham. The car is unlikely to handle the same on both and the reduction in front tyre width will certainly have an effect. Why did you swith to A048s if the handling was fine or CR500s? Link to comment Share on other sites More sharing options...
Graham Sewell Posted June 21, 2004 Share Posted June 21, 2004 Just a thought that no-one has mentioned - moving from the same tyres all round, to ones that are 20mm wider at the back will also raise the back by 12mm - giving a total rake of 27mm instead of 15mm. I would expect this to cause some changes to handling - probably oversteer rather than understeer though. Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
Gambo Posted June 21, 2004 Share Posted June 21, 2004 I had a similar problem when I went to 032's with my hpc. Bought nice new image wheels, different ofset front to rear.This had the effect of increaseing the rear track in relasion to the front. caused no end of understeer, untill I wide tracked the car. that seemed to have sorted the car. the theory is that a car's front and rear track should be the same or slightly wider on the front, to help turn in. might be talking B**&L£cks but my car is better now. Link to comment Share on other sites More sharing options...
Mike C. Posted June 21, 2004 Share Posted June 21, 2004 I've run my Superlight on various 13" tyres - ACB10s, CR500s, 32Rs, 21Rs and recently 48Rs, and they all have slightly different characteristics, which take time to get used to. I went for 175/60 fronts and 205/60 rears. This lowers the front slightly and, with the stiffer side walls, seems to give very quick turn-in. I've always had some understeer, but the 48Rs are no worse, probably better, than the others I've used. On road and track I'm very pleased. I will experiment with pressures, but I currently run 18 rear, 19 front (cold). Mad Manx Link to comment Share on other sites More sharing options...
frankyknuckles Posted June 21, 2004 Author Share Posted June 21, 2004 Why did you swith to A048s if the handling was fine or CR500s? Better ride characteristics (less tram lining, better over bumps etc) Reportedly better handling characteristics with 13" rims. Wider choice of cheaper tyres. (yokos are half the price of CR500's) will also raise the back by 12mm As I say, my car was flat floored at CC with a 15mm drop back to front, I calculated that the new wheel tyre combo would raise the rear by approx 10mm and drop the front by about 2mm, hence increasing the rake, maybe by a little too much. I say this bacuse I got a back end twitch going round one corner that I did not (and would not) expect to happen before the wheel tyre change. I think I need to get the freestyle and have it flat floored while I pick Garys brains about setup (and maybe get an adjustable Front ARB). www.R300.net Link to comment Share on other sites More sharing options...
frankyknuckles Posted June 21, 2004 Author Share Posted June 21, 2004 my origina thread on ride height change can be seen here www.R300.net Link to comment Share on other sites More sharing options...
frankyknuckles Posted June 21, 2004 Author Share Posted June 21, 2004 I've just measured theheight of the chassis above ground. Lower outer side chassis rail just behind lower front wishbone - 12cm End of same chassis rail just in front of rear wheel - 16cm Some adjustment needed there me thinks www.R300.net Link to comment Share on other sites More sharing options...
Jason Plato Posted June 22, 2004 Share Posted June 22, 2004 Trouble is franky , if you lower your back end the understeer will get worse . ☹️ Link to comment Share on other sites More sharing options...
frankyknuckles Posted June 22, 2004 Author Share Posted June 22, 2004 yeah I know, but I would like Gary at Freestyle to give it the once over and get everything setup as it should be, at least I then have a reference point to start adjusting from if I still don't like the handling. www.R300.net Link to comment Share on other sites More sharing options...
dino ferrana Posted June 22, 2004 Share Posted June 22, 2004 I have just noticed that you now have wider rear tyres than front. This will inevitably change the balance of the handling. The increase in rear grip may be causing the front end to push on. Link to comment Share on other sites More sharing options...
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