Shudder (at speed)

Post by **rayofleamington** » Wed Jun 23, 2004 6:41 pm

That could cause a vibration as the diff struggles to cope with wheels revolving at different speeds.

The wheels will always revolve at different speeds however on a straight road the difference will be very small (even just from a small psi difference). If the diff is that bad that it gives a vibration then you would spot it on cornering at speed.
If the mechaniac had mixed up the tyres you would heve other things to worry about (like getting round bendy A-roads in one picee)

If CW keep messing with propshafts then I would still suspect gearbox rear bush has got very worn.

Post by **brixtonmorris** » Wed Jun 23, 2004 7:02 pm

how about a failing water pump bearing or a week fan blade.
get hold of the fan blade and check if there is movement from side to side.
it can cause resonance at speeds

Post by **Pyoor_Kate** » Wed Jun 23, 2004 7:16 pm

Fan blade: Not noticably. Although I have a notorious history with waterpumps on cars.

Wheels: They were still in pairs, 145R14 on the front, 155R14 on the back. Both front ones were Kumho and both the rear were Firestones. One of the Firestones is very unevenly worn.

I've just swapped them so that the fronts are now the 155R14s and the rears are now the 145R14s....

With the traffic being so awful today I didn't get up to 70 to do the whole "pull over and check if the tyres are bullging" thing.... so maybe that'll be tomorrow...

Post by **rayofleamington** » Wed Jun 23, 2004 8:41 pm

One of the Firestones is very unevenly worn.

in which way is it uneven? is it less tread on inner (or outer) edge continously around the diameter
or unevenly worn in patches or some inner / some outer?

Post by **Pyoor_Kate** » Wed Jun 23, 2004 8:45 pm

Continuously and evenly less tread on the outer edge of the now front passenger side (was rear passenger side) wheel. It's the one that was on there when the suspension / toe in / whatever got knackered the first time. It's still *just* legal on that strip... It was rebalanced after the tyres were swapped around....

Post by **brixtonmorris** » Wed Jun 23, 2004 8:55 pm

tyres worn on edges is caused by worn track rod ends,...................... or tracking.
the worn track rod end is on the oppersite side to the edge worn tyre.
a worn track rod end could cause a vibration at speed weather the wheel is balance or not.
the vibration cause's the tyre to wear out on the edge.
(not sure if this is whats going on here though)

Post by **Pyoor_Kate** » Wed Jun 23, 2004 9:01 pm

Well, the uneven wear has stopped since the supension setup was all redone.... It's just still this shudder.

Post by **brixtonmorris** » Wed Jun 23, 2004 9:07 pm

has it had new track rod ends fitted

Post by **Pyoor_Kate** » Thu Jun 24, 2004 11:40 pm

Checked the tyres today, no bulges.

However, swapping the front and rear tyres seems to have done the trick. I must presume that those nasty Kumho tyres (on the front) were the cause of my problems...

Ta for advice peoples...

Post by **Chris Morley** » Fri Jun 25, 2004 1:55 am

I wonder what it was about those tyres that caused the problem? Perhaps they cope better at the back because there is less weight to cope with? Also the solid rear axle & springs might dampen their natural tendency to wobble?

Post by **rayofleamington** » Fri Jun 25, 2004 10:45 am

Checked the tyres today, no bulges

How did you check them?
Sometimes bulges are hard to spot so one method is to jack the wheel a few mm off the ground then rotate it. If it is significantly out of shape you will see it touch the ground but another thing to watch out for is if there is and distortion 'wobble' at the sides.

Post by **Matt** » Fri Jun 25, 2004 11:40 am

nasty Kumho tyres

I've got 3 of them an 1 firestone, they arnt bad at all!

Post by **rayofleamington** » Fri Jun 25, 2004 11:49 am

nasty Kumho tyres

I've got a pair of them as well - presently they are leaning against the fence, but for the last year they were used as ballast to hold down car cover. Given the choice I wouldn't use 155's on standard rims as I think the effect on handling is close to dangerous so I'm only keeping them for an emergency.

Post by **Matt** » Fri Jun 25, 2004 12:24 pm

My Kumhos are 145's.....

Post by **rayofleamington** » Fri Jun 25, 2004 12:55 pm

My Kumhos are 145's.....

and so are Kate's but, so? ;-)
I was reffering to Kate's 155's regarding the negative handling, as she might be tempted to go and buy some more 155's to match the 'ok' Firestone 155s.

Post by **Chris Morley** » Fri Jun 25, 2004 2:11 pm

I wouldn't use 155's on standard rims as I think the effect on handling is close to dangerous

Ray, I think you need to elaborate on this statement because the various Minor specialists that sell 155s clearly don't agree. I replaced the fairly worn 145s I inherited on the rear with new 155s. The result was far less axle tramp in the wet, a great reduction in the tendency to fishtail the rear end when applying power and a more predictable feel when cornering (the 145s felt like they were hopping and skipping). So in my case 155s improved the handling no end. Of course this single example may not be representative. Is your opinion based on one set of Kumho 155 tyres?

Some people are of the opinion that 155s might be more likely to pull away from the wheel rim under extreme cornering. To my mind if you're pushing that hard on a public road you're about to have an accident anyway.

Post by **Pyoor_Kate** » Fri Jun 25, 2004 3:17 pm

It must be said changing from the 145's to the 2 155's / 2 145's, when I first changed a pair of tyres on the mog seemed to majorly improve handling - however it made the steering noticably heavier.

I'm afraid checking the tyres was purely done by feel, and looking without jacking. At 6 am, on my way to work I'm very unlikely to jack my car up!

And I wanted to do it as soon as possible after coming off the motorway.

I will, I suspect, change the tyres on the rear of the car as soon as I can afford to, because I don't, well, trust Kumho. I've had enough of cheap tyres - the only reason they're on there is 'cos the Mog Centre fit them, and I forgot to say "not Kumho" last time I went...

Post by **rayofleamington** » Fri Jun 25, 2004 7:49 pm

My renewed opinion was based on the Khumo 155's. I replaced them with some partworn 145 Michellins (thanks Willie) and the imrovement to handling under 'harder' conditions was huge.

Some people are of the opinion that 155s might be more likely to pull away from the wheel rim under extreme cornering. To my mind if you're pushing that hard on a public road you're about to have an accident anyway.

Exactly - so when you have to do a hard swerve to avoid an accident I'd rather have 145's and avoid the accident than have 155's and play russian roulette. The same applies on country roads, for example when a bend gets tighter than you expect.
If you have a fat tyre on a thin rim it is basic mechanical priciples that the car will have a bigger tendency to go straight on when you corner.
The Kuhmo's vs Michelins were probably a biassed example as a good brand of tyre will be better than a rubbish one, however given the same brand condition and age of tyre on a stndard minor rim, there is still no way a 155 will give as good cornering as a 145. I've bought a few cars with 155's and they all had reduced handling as a result.

because the various Minor specialists that sell 155s clearly don't agree.

surely the Moggy centres sell 155's and 165's for peope with Van rims?
As for tyre technology, if you don't think I'm right then feel free to ask an engineer at Dunlop etc.. who I would bet plenty of money will also agree that 145's will be safer than 155's on standard rims.

Post by **Gareth** » Sat Jun 26, 2004 2:40 pm

Not that we're off-topic by any means...

...but I've got 155's on Phyllis and she handles like she's on rails. Much more fun to drive, and feels much safer than our FWD Metro... ah, perhaps that's not a good comparison... er...

Post by **57traveller** » Sat Jun 26, 2004 3:59 pm

145's on my saloon (5 yr old Khumo) but 155's recommended and fitted by a Minor specialists. Much prefer the 155's feel far safer and surer.
Wouldn't have thought that tyre size determines a cars tendency to carry on. Depends more on mass and speed of vehicle surely. There may be a slight gyroscopic effect from the wheels but not enough to overcome the momentum. Messrs Newton, Hooke etc. It's a few years since doing any of that so may be a bit rusty.