robmar Posted October 13, 2004 Share Posted October 13, 2004 in relation to DaveJ's thread about exhaust protrusion in terms of sprinting is it better to go for the wider tyres, especially at the rear I have a choice for when I get my new tyres(next year) to either replace with similar width 7" on 6.5" rims or go wider as I have some of the wider MB rims which I can put on sitting in the garage 😳 I am not really interested in a debate of 7" is fine for 135BHP BTW rob Link to comment Share on other sites More sharing options...
Adrian Williams Posted October 13, 2004 Share Posted October 13, 2004 Rob I'm no expert as you know but I would suggest it depends on how you want to define 'best'. If wider rubber equals more grip then starts should be improved but I suspect you might loose some chassis balance. This could always be adjusted back again with ride height etc. What you should do is run 22" rears and not the 21" you had this year, I'm told the extra height in the sidewall has more 'give' and therefore better traction. For what it's worth I run 7" MB rims at the rear rather than the standard 6.5 or 8.5. Adrian Edited by - Adrian Williams on 13 Oct 2004 14:20:32 Link to comment Share on other sites More sharing options...
robmar Posted October 13, 2004 Author Share Posted October 13, 2004 best as in quickest yep was going to 22's as this seems the norm rob Link to comment Share on other sites More sharing options...
Adrian Williams Posted October 13, 2004 Share Posted October 13, 2004 Quickest where? Start Brakes Corner entry Corner exit Straights (not desperately relevant) or overall 🤔 Take your pick Adrian Link to comment Share on other sites More sharing options...
robmar Posted October 13, 2004 Author Share Posted October 13, 2004 everywhere as in at the end of the dya a quicker time maybe it is an unaswerable question with too many variables rob Link to comment Share on other sites More sharing options...
Adrian Williams Posted October 13, 2004 Share Posted October 13, 2004 I'll stop playing devils advocate and let someone better qualified answer your original question. 😬 Adrian Link to comment Share on other sites More sharing options...
david nelson Posted October 13, 2004 Share Posted October 13, 2004 Rob we would be happy if your were quicker at the start line, but slower than me at the finish 😬 I think I will be on 22 at the back David Link to comment Share on other sites More sharing options...
Bilbo Posted October 13, 2004 Share Posted October 13, 2004 Hi robmar Well depends on the age of the car. 8.5 rims will not fit on mine need to have later de-dion and bars or they foul. I can just about get away with MB 7.5" rears. Even then I need 3 mm spacers ❗ They are as MB R500 8.5" outside section and narrower inner section of the rims. Having clam wings I have 6.5 " front but the outside and inner wheel sections are different. The front are as the rears not narrower as the MB R500. If you have thoese nasty cycle wings you can not do this.... 😬 Normally the outside sections are different width and that means they look different. Also mine makes the car 1" wider on the front. 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? engineered by Roger King, on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Link to comment Share on other sites More sharing options...
Brodie Posted October 16, 2004 Share Posted October 16, 2004 Hi Rob-Ialways remember thinking that it wouldn't matter much not having the largest mag rims and widest ACB 10's on my Fireblade,but it did!!Even a light car benefits from the widest,stickiest rubber available! '......in yer bike!' Link to comment Share on other sites More sharing options...
robmar Posted October 16, 2004 Author Share Posted October 16, 2004 fatter it is then Link to comment Share on other sites More sharing options...
david nelson Posted October 17, 2004 Share Posted October 17, 2004 No Rob you have miss understood, you need very thin tyres not fat ones 😬 David Link to comment Share on other sites More sharing options...
kpm Posted November 5, 2004 Share Posted November 5, 2004 Whilst on the tyre subject are the CR322 the best tyre for a novice in a 1.6vx in terms of the classes. I assume these tyres are mandatory in the most basic class ? Link to comment Share on other sites More sharing options...
robmar Posted November 5, 2004 Author Share Posted November 5, 2004 there are no control tyres in the l7 championship basically the classes are split class 1&2&4 - list 1a tyres class 3&5 - list 1b class 6 - non road legal with a 1.6vx you can go into classes 1, 2 or 3 depending on spec I have no idea about cr322, are they the academy control tyre 🤔, in which case they are list 1a so classes 1 & 2 are for you, but you may also be eligible for class1 rob Link to comment Share on other sites More sharing options...
Silver 21 Posted November 5, 2004 Share Posted November 5, 2004 Rob Haven't really contributed to this so far but if you talk to people like BMTR they will tell you it is possible to overtyre a car for Hillclimbs and sprints. Its a fine balance between power and grip. When I ran my previous car(not a caterham) it had 205's on the rear and their advice was that they were simply too wide for the power available, (too much effort for the engine to move additional contact area or something similar and would outway the benefits of the extra width). When fitting my set of ACB10's they adviced not to go any wider than 7" on the rear with 140bhp for the reasons mentioned above. With bike power I will be sticking to 6 x 21 on the front & 7 x 22 on the back *thumbup* No doubt someone will come along to argue with all of the above so I'll shut up now, 😬 😬 Graham Competition Secretary 2005 Speed Championship - 12 Events and Growing Link to comment Share on other sites More sharing options...
david nelson Posted November 5, 2004 Share Posted November 5, 2004 BB Are you saying that if Rob uses wide tyres he will go slow as the 1.6 K has not got the power for them? or he will go slow if he uses thin tyres couse he has to much power 🤔 🤔 David Link to comment Share on other sites More sharing options...
robmar Posted November 5, 2004 Author Share Posted November 5, 2004 but what if I have 150, 160 or even 170 bhp 🤔 😬 all on the standard plenum of course rob Link to comment Share on other sites More sharing options...
david nelson Posted November 5, 2004 Share Posted November 5, 2004 Rob hope all is well please see my comment dated 17th October. David Link to comment Share on other sites More sharing options...
david nelson Posted February 9, 2005 Share Posted February 9, 2005 Well thinking about what class to go into this year. If I am going to stay in class 3 what size ACB10's do I need. Front 6.0/21.0-13 Rear 7.0/22.0-13 🤔 🤔 David Link to comment Share on other sites More sharing options...
Adrian Williams Posted February 10, 2005 Share Posted February 10, 2005 David assuming your front rims are 6.5" I'd go to 7" at the front so Front 7.0/21.0-13 Rear 7.0/22.0-13 You might consider going to 8" at the rear bearing in mind all that extra power you 1800 boys have got Adrian Link to comment Share on other sites More sharing options...
robmar Posted February 10, 2005 Author Share Posted February 10, 2005 probably not far off FWIW I ran 7/21/13's all round for the last 2 years but that was more to do with what tyres came on the wheels 2nd hand this alo meant I didn't have to change setups as my road and slick tyres where also of the same diameter I am planning to run 7/21's at the front and 7/22s at the rear this year when I get around to ordering some[:] rob Link to comment Share on other sites More sharing options...
Jason Plato Posted February 10, 2005 Share Posted February 10, 2005 what harm would 8" or wider on the rear do ? so long as the width of the fronts were matched , just plays devils ad' . Dave Link to comment Share on other sites More sharing options...
robmar Posted February 10, 2005 Author Share Posted February 10, 2005 Daeve - I would debate that with only 140 bhp (MAX) that a supersport car would be able to get enough heat into them over a short sprint.... Link to comment Share on other sites More sharing options...
david nelson Posted February 10, 2005 Share Posted February 10, 2005 Just called BMTR and got some prices. 7/21/13 £103 +Vat 7/22/13 £110 + Vat prices include fitting. Any found a better price? David Link to comment Share on other sites More sharing options...
robmar Posted February 10, 2005 Author Share Posted February 10, 2005 David - I have always gone direct to AVON, but then had to have them fitted (5-10 quid a corner) so those prices don't look too bad... I have a number somehwere.... 01225 357694 - ask for Brian Davies Rob Link to comment Share on other sites More sharing options...
Adrian Williams Posted February 10, 2005 Share Posted February 10, 2005 I bought mine from BMTR last year, couldn't get a better price anywhere else. They also use neat ali valves and stick on weights, they spend their time working with spun ali rims and are unlikely to ruin your nice MB wheels. Adrian Link to comment Share on other sites More sharing options...
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