Tyre Profiles

[terrymcg]

Does anyone know what the harm or detremental effects would be in fitting a 225/35/18 tyre to the front of the car rather than a 225/40/18? I take it that the speedo is slightly/badly knocked out?? Anything else?

 

[Stratman]

The cruise control will probably drop out at higher speeds.

 

[renault12ts]

The diameter of your tyre will be nearly an inch greater. Why do you want to do this?

 

[mazza]

Does anyone know what the harm or detremental effects would be in fitting a 225/35/18 tyre to the front of the car rather than a 225/40/18? I take it that the speedo is slightly/badly knocked out?? Anything else?

225/40/18
Rolling Radius: 200.18 cm
Total Diameter: 63.72 cm
Sidewall Height:9.00 cm

225/35/18
Rolling Radius: 193.11 cm
Total Diameter: 61.47 cm
Sidewall Height:7.88 cm

actual speed will be less by 3.5% compared to indicated speed

you will be loosing tyre sidewall height...so ride will be slightly harder...but probably grippier in corners (ensure pressures are spot on).

thats about it really

mazza

 

[whitenemesis]

Possibly unbalance the handling slightly by changing the relative stiffness front to rear?

 

[crockers]

If you speedo is on the limit of it's 10% accuracy would the car still be legal?

 

[whitenemesis]

Speedo will be over-reading (i.e. fast) so potentially saving you from speeding?

 

[rf065]

Lot of assumptions here, but you are talking about changeing the front tyres only? Do you already have a staggered wheel set up? If you do there may already be a discrepency between front & rear tyres that will be exagerated if you change the fronts.

Russ

 

[whitenemesis]

IIRC MB introduced the staggered setup specifically to create the difference in stiffness. This provides a safe handling characteristic without undue change in ride.

 

[terrymcg]

Yes I already have a staggered set up, 255/35 on the rear and 225/40 on the front. i just dont like the look of the 40's on the front - they look like tractor tyres compared to the rear in my opinion.

Just wondered if there would be any harsh side affects of sticking a 35 on the front - obviously it will still be staggered just a different profile. So a harder front end.

 

[rf065]

As standard the discrepancy between front & rear is only 0.2%

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 225/40-18 3.5in 12.5in 25.1in 78.8in 804 0.0% 255/35-18 3.5in 12.5in 25.0in 78.6in 806 -0.2%

Changeing the fronts to a 225/35 will alter this to 3.4%, possibly more than the electronic safety systems would like, you would need to try it first to be sure, Expensive exercise if it does not work though.

Russ