Nasty handling with mix and RFTs

[RenoHuskerDu]

Nasty is not strong enough. Evil is better. I replaced 2 worn front Bridgestone Dueler RFTs with Uniroyal RainSport 3 SUV in 255/50-19Y.  The Uniroyal is very popular in FR and Germany recently, with demand outstripping supply due to a recent comparison test win in car magazines here. In good discipline, I rotated tires so the new ones were on the back.

But putting the non-RFTs on the back was a big mistake. The car feels 'loose' and actually oversteers if I turn off ESP! With ESP on, the system springs into action on every twisty bit like an overzealous proctor at a prep school exam. The Uniroyals are slightly smaller, so the ESP computer must sense that F/R speed diff as a dangerous condition. It absolutely kills the fun, cutting the power and applying the brakes on one side of the car.  I tried running the active drive in non-sport mode; no better.

I just rotated F to R so now I have the RFTs on the back and the new Uniroyals on the front.  I'll let you know how that works out after getting back from work this eve.

I also just ordered 2 more Uniroyals, and you can start with the silly frog yank jokes now. I deserve them. There is something about the 'merican culture that makes us tend to rush into things too quickly.

[535dboy]

Surely the clue is in the title!!

Mix set up is dangerous.

[RenoHuskerDu]

Yes I shoulda googled first. Shouldacouldawouda... 

Update: It's much better with the stiff-sidewalled RFTs on the back. They are only about 25% worn so even in very heavy rain today the car felt stable.  I also diddled the air pressure balance a tad, with 2.6 up front and 2.7 in back. I've been in France so long that I've stopped thinking in psi.

[Finglonga]

Should have replaced all 4 at the same time, in UK it would invalidate the insurance as it as said is dangerous. Chances are if pulled by the police the car would not be going anywhere apart from on the back of a recovery truck.

[Beanfest2]

Rft,s and non rft an offence  really.?  Not heard that before.


Insight electrical ltd.    &.  Bristol soundsystem hire

[RenoHuskerDu]

[quote="Beanfest2"]
Rft,s and non rft an offence  really.?  Not heard that before.
[/quote]

As bad as the handling was, it makes sense. But since when do laws make much sense? Consider cookies...

Now that I put the RFTs on the back and the new Uniroyals on the front, the handling is once again sorted. But turn-in is not as crisp as before. I'll be screwing on the other pair of Uniroyals this week, assuming the French go off strike long enough to deliver my tyres.  )

[kjb1]

[quote="Finglonga"]
Should have replaced all 4 at the same time, in UK it would invalidate the insurance as it as said is dangerous. Chances are if pulled by the police the car would not be going anywhere apart from on the back of a recovery truck.
[/quote]

It is not illegal to run run flats on the same axle and normal tyres on the other.  In pairs 100% legal

[kjb1]

if honest it no doubt is not illegal to run one runflat and one normal tyre on same axle as long as both are legal etc

[X5Sport]

No that is illegal.  Tyres must be of the same 'type' on the axle.  RFTs are not the same as standard radials so that is an illegal mix.  Section 4.1.2 of the MOT if you want to look it up.

Richard

[kjb1]

well i knew it wasn't illegal to run on separate axlesp

[martin33100]

For reference it wont apply to an E70 but it is illegal to have run flat tyres on a non run flat car.

[X5Sport]

Says who?  They use the same rims and if the car has a tyre pressure monitoring system then there is no problem.

My E53 had standard rims with Bridgestone RFTs fitted.  It had the normal BMW TPMS via the ABS fitted and working.

It may be illegal without TPMS, but otherwise it's fine.

Richard

[martin33100]

[quote="X5Sport"]
Says who?  They use the same rims and if the car has a tyre pressure monitoring system then there is no problem.

My E53 had standard rims with Bridgestone RFTs fitted.  It had the normal BMW TPMS via the ABS fitted and working.

It may be illegal without TPMS, but otherwise it's fine.

Richard
[/quote]I was referring to a non run flat car that didn't have the TPMS fitted as standard.

[RenoHuskerDu]

I hope it's not EU-wide where it's illegal to run RFTs on older cars. I plan to start running RFTs for winter tyres as we replace them on the family fleet. The thought of dealing with a flat tyre in freezing temps is enough to curl Juan's hair. Our winters in Alsace can be quite nasty.

[X5Sport]

As long as you have a TPMS fitted then you should be fine.  It's illegal to run RFT without some form of tyre pressure system that tells the driver immediately that there's a pressure loss.

The statement in the post #10 above was too broad and was corrected.

Richard