Argyll Posted September 9, 2007 Share Posted September 9, 2007 Am I right in thinking the tyre profile must be the same front and rear? Quote Link to comment Share on other sites More sharing options...
Argyll Posted September 9, 2007 Author Share Posted September 9, 2007 I don't understand why my post was edited!!! Bump does anyone know the answer to this? Quote Link to comment Share on other sites More sharing options...
Sarnie Posted September 9, 2007 Share Posted September 9, 2007 I don't understand why my post was edited!!! Bump does anyone know the answer to this? You don't have to have the same profile but it is adviseable to keep the profiles the same as oem spec Quote Link to comment Share on other sites More sharing options...
Zzzz... Posted September 9, 2007 Share Posted September 9, 2007 sounds very general this question. Can you elaborate what information you are after and why? e.g Do you want to know why the profiles are 45 on OEM but look different? Do you want to go smaller profile on the RR to match the front look? Do you plan on going 19" on the RR and 18 on the FR? Are you worried about the effect on rolling diameter etc...? This would help focus the answers you are after... Quote Link to comment Share on other sites More sharing options...
Argyll Posted September 9, 2007 Author Share Posted September 9, 2007 I had Kumho Ecsta K11's (235/50/17) put on the back and they are terrible!!! I currently have on the front 225/50/17 (Don't remember the brand). I was looking to fit either Toyo Proxies or Falken 452's of the same size as a replacement for the rear tyres. But neither firm make them in 50 profiles, they only make them in 45 profile. So I want to know if it is safe to have either Proxies or Falken 452's 245/45/17 on th erear and 225/50/17 on th efront? I'm sure I read somewhere that this would cause problems but I can't find the post now. Quote Link to comment Share on other sites More sharing options...
Zzzz... Posted September 9, 2007 Share Posted September 9, 2007 There is no safety issue as such.... but it is not advisable to mix and match tyres... that's the first advice... but again it is not ilegal or unsafe... only that it can have an effect in the handling of the car. On the RR axle you are changing the rolling diameter of the wheels Original 235/50/17 = 2095 mm circumference New proposed 245/45/17 = 2049mm circumference a difference of 2.2% on wheel tyre combination... So when your speedo reads 70mph, you're actually travelling at 71.55mph not a big difference ... so you can get away with it... So the profile alone will not have a safety effect, i think the biggest concern you should consider is the mixing of brands of tyres and the possible effect on handling of the car... Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 9, 2007 Share Posted September 9, 2007 I don't understand why my post was edited!!! Bump does anyone know the answer to this? Was you post edited? Looks like TheMinel edited his own post. Anyway, I'd agree with Zzzzz up to a point but I'm not sure whether the change in rolling radius would have an adverse affect on the traction control etc. Might be time to upgrade to some bigger wheels - plenty have gone from 18" to 19" on here so there should be some cheap 18s knocking around for sale. Quote Link to comment Share on other sites More sharing options...
Argyll Posted September 9, 2007 Author Share Posted September 9, 2007 Why though? What great benefit would it create to me? Quote Link to comment Share on other sites More sharing options...
bronzee Posted September 9, 2007 Share Posted September 9, 2007 If I'm reading this right, my 2 cents worth. One of my friends has an pre-loved 2003 Jap import 350. When he purchased it had tyres that had a different rolling radius than stock rolling radius, quite a bit different, and totally wrong size on the front. This used to send his TCS/VDC absolutely nutty on a very regular basis, especially overtaking and cornering, not the most desirable times at all. Hopefully this little cautionary tale has helped. Quote Link to comment Share on other sites More sharing options...
Sarnie Posted September 10, 2007 Share Posted September 10, 2007 Why though? What great benefit would it create to me? Apart from looking miles better than a set of 17's it may not cost you much more than about £500 if some one has a set of standard rims or if your lucky a set of rays Personally I'd go straight to a set of 19's and you can get some reasonably priced for less than £1k This was my zed on 19's: Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 10, 2007 Share Posted September 10, 2007 Why though? What great benefit would it create to me? Just that the 17"s look a little lost in the arches of a Zed. IMHO of course. Quote Link to comment Share on other sites More sharing options...
Sarnie Posted September 10, 2007 Share Posted September 10, 2007 Why though? What great benefit would it create to me? Just that the 17"s look a little lost in the arches of a Zed. IMHO of course. Probably the reason why they stick tyres with a 50 profile on them Quote Link to comment Share on other sites More sharing options...
Zzzz... Posted September 10, 2007 Share Posted September 10, 2007 Always, the styling is decided and wheel and tyres specified at the early stages of the concepts, it is then up to the ride andhandling experts to tune the TCS, ABS etc... The TCS can go wild if the rolling radius has changed in relation to each axle (~FR and RR)...so going round a corner, for example, the fronts will be turning at some rate and if the RR are bigger and turning at a slower rate, the TCS will think the Fronts are slipping and try and slow them down, when in fact they are perfectly ok... and this will apply also to each wheel corner, also you then have the effect of g sensors, new wheel and tyres might allow you to pull more cornering "G" and I think the TCS ESP thingy is tuned to detect certain "G" levels at which point it starts to judge that you are going "too fast" for the corner... so it can cut in ... Aim to keep the rolling radius as close as possible to the original dimension and you should be ok (FR and RR) ...as for cornering G etc... if the wheels and tyres are correct size, the effect should not be so noticeable...my opinion anyway... Quote Link to comment Share on other sites More sharing options...
Argyll Posted September 10, 2007 Author Share Posted September 10, 2007 Maybe I'm wrong but i think some people replying to my post are referring to if I changed the tyre size at the front. If so I'm not! I'm only talking about changing the profile from 50 at the back to 45. All my wheels would still be 17's. Quote Link to comment Share on other sites More sharing options...
Argyll Posted September 10, 2007 Author Share Posted September 10, 2007 Why though? What great benefit would it create to me? Apart from looking miles better than a set of 17's it may not cost you much more than about £500 if some one has a set of standard rims or if your lucky a set of rays Personally I'd go straight to a set of 19's and you can get some reasonably priced for less than £1k This was my zed on 19's: Yeah £1000 for the alloys but I'd still have to buy new tyres for it too! Quote Link to comment Share on other sites More sharing options...
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