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MG MGB Technical - Skidding in the wet

Afternoon all,

My '73 GT is terrible in the wet. Anything more than slightly moderate braking causes the front brakes to lock up, making for quite dangerous driving.
I've already changed the pads but that's made no difference. The tyres are some make I haven't heard of before and they are 165's - I'll be replacing them soon so I may put some 185's on there to help.
Any other ideas as to what could be causing this - or is it normal??

Thanks,
Matt
MattWilkinson

If your brake disks are in good condition I would tend to believe it's the tires. You might want to check that the rear brakes are working correctly, if not the fronts are taking all the braking load which may cause some of the skidding.
John H

Let's face it, traction under braking is first determined by the friction between the tire (tyre) and the road surface. If the brakes will lock up the wheels then the problem is in lack of friction between the tire and road. Going to a wider tyre will help in the dry, but in the wet it's much more important to have a good tread design to aid in getting the water from between the tire and the road surface so you don't hydroplane. For wet weather performance look for a tire with a combination of wide grooves between the tread blocks and if possible some type of directional design which aids in water removal. Any tire that's good in the wet is going to compromise the dry performance, so it's a balance. Decide which conditions you normally drive in and go from there. This tire from Michelin looks like a pretty good compromise between dry and wet performance and is available in a 185-70R14 http://www.michelinman.com/tires/passenger-car-minivan/hydroedge/86134/


Bill Young

How old are the tyres? If over 6 years -change them irrespetive of the amount of tread! M
Michael Beswick

I agree that the width of tire may help in the dry, but wet, depending on the depth of the puddle, your traction may be worse.

That said, I had old tires and they scared the crap out of me in the wet. Changed to new Kumho's - kind of an unheard of brand, and what a difference! I would say buy tires with a lot of "siping", little grooves that do a LOT for wet traction. You can even have your present tires "siped", but I don't have any experience with that.

Rubber compounds vary, and it seems the higher winter traction (maybe not wet road traction) tires have a shorter life, as the rubber is softer.

Is there any real rubber in tires anymore? Or belts, by the way. I put a new serpentine belt on the family cruiser and it squeals irritatingly. Put the old one back on today - ahh. The new one is now the spare. I've heard lots of squealing belts on other people's cars, too.
Tom

I think the problem may well be the age of your tyres. I put Kumho 165/80 tyres on my MGB six years ago, and they were excellent in the wet. But this autumn they skid as soon as the road is more than a little damp. There is plenty of thread, but the rubber has hardened.

Some years ago I had a very scaring moment with my midget. During a shower the car completely lost its grip, it was like driving on ice. When I looked, the tyres turned out to be 13 years old...

It has been said a lot of times before, BMW and other manufacturers advise never to drive on tyres that are more than six years old.

Personally, I like to stay with the 165 dimension. I think it looks right, the MGB tracks so beautifully on rough roads, and the steering is not heavier than it has to be.

As far as my experience goes I can highly recommend the Kumhos, but this time I have ordered Vredestein Sprint Classics that will be put on during the winter. Vredestein recently introduced tyres in "our" dimension, 165/80-14. I know a couple of MGA and Healey owners that are extremely happy with their Vredesteins. And they look sooooo cool!

Tore


Tore

I'm using michelin XM1's,
Really good
http://www.jaxquickfit.com.au/other-tyre-news-michelin-energy-XM1.htm?OVRAW=Michelin%20xm1&OVKEY=michelin%20xm1&OVMTC=standard&OVADID=12563930541&OVKWID=110273363541

I was using "INTENSA" tyres, that nearly killed me. Tiniest bit of wet and it was like the ice-capades
Peter

Actually, that's a good point about the age of the tyres.

They don't have a profile value, they're just marked as 165SR14 so I'm guessing they're pretty old (they were on there when I bought the car).

Does anyone know when this type of tyre measurement was phased out?

Thanks
MattWilkinson

Matt,

I have a set of Michelin MX tyres on my 69. They are marked 165R14 ie pre the practice of designating the profile size in the marking eg 165/80R14. They are on original wires.

They are marked as made in France and have a dot code of (here I duck for cover from the flack advice that may well and reasonably follow) FN J1 B4Bx474. Yes, I really do know what that means!

Recently I have been working on a range of issues associated with preparing this car for some serious touring away from home. Wheel type, tyre options (including sans tubes) et al have been high in my thinking. These tyres have 4.5 to 5mm of tread depth on them and on our local (excellent) roads they have been fine, especially given that I don't have any sporting aspirations for this car or in my driving style. We have also been experiencing years of serious dry - I mean bugger-all rain seasons. I suspect that has helped because I probably last drove this car in genuine rain in 2001.

The point is I have closely inspected the tread surface of these tyres and, to be frank, they look and feel (to the thumb nail test) like hardened plastic. I know they have suffered from age not withstanding that they have tread depth. A few years ago I replaced the tubes and did an inspection of the tyre inner surface at that time. They were visually fine, no sign of cracking or wear. Same on the exterior.

End of the day though I know I am driving on aged (very) tyres. I have recently run this car in the 90+mph range testing tuning issues but I realised I was thinking tyres when I was doing it. I will be changing tyres (with whatever wheel selection) before I ever take it back to those speeds again.

Not sure of the date of the change in tyre designations nor the introduction of dot codes, but if yours are marked like mine.....?

Do yours have a DOT code? If so, what is it?

Regards
Roger


Roger T

Tore,

I am in agreement concerning the look of 165R-14 on the MGB. We are also looking at Vredestein to replace my 12-year old Goodyear Intrepid's on our B/GT. A month ago I drove 650 miles through heavy rain, and slick roads through the mountains (Western PA) all the while concerned about slippage that never occurred.

Our tire vendor has looked at the tires on our B/GT, and says because the car parked inside except for weekend and holiday drives we have very little exposure to the sun, and (UV) distruction of the rubber. Not sure how much of a factor this is, but the tires do not look, or perform their actual age.

Regards,

Larry C. '74 B/GT & '69 Midget
Larry C '69 Midget

Definitely tyres will have a greater impact on grip than brakes. I had a new pair of tyres on the back and they were terrible for breaking away in the wet, so bad I had to swap fronts and rears. They were USA Generals, and a friend in Sacramento said even though he could get an employee discount on them no one bought them as they were too hard, even for California, let alone cold and wet Blighty. I've never heard anyone complain the brakes were too effective (at locking) on the MGB before, usually they try to improve it by putting bigger calipers and pads on, blissfully unaware that braking effect is primarily down to the tyre patch as has been said. In fact unless you uprate the rears as well you *reduce* the overall braking effort, as if you can lock the fronts with lower pedal pressure then the rears are getting lower pedal pressure as well and hence aren't retarding you as much as they were before. I wonder if a PO has uprated the fronts. The other thing is that suddenly banging the brakes on *will* cause them to lock more easily than progressive braking, as there isn't enough time for weight transfer to put more weight on the fronts before they have locked, and once locked it will stay locked until released (or the surface changes radically). There is said to be a date code on the tyres near the rim as part of a string of characters prefixed DOT. Before 2000 it was a 3-digit code, after that a 4-digit. But I can't see that on any of my V8 tyres, even though according to my records the last ones were replaced in 2001.

"Does anyone know when this type of tyre measurement was phased out?"

Not sure what you mean by this, 'standard' tyres have an aspect ratio of 82% and this wouldn't be marked, it is only when the ratio reduces i.e. typically 70 for commonly available tyres available for an MGB today that you would get 165/70HR14. I have 185s on the V8 and that is about the biggest you can get in the boot of a GT and still fasten the cover. You will make the steering noticeably heavier at parking speeds going from 165s to 185s. You shouldn't need any more than 165s if the tyres are not time-expired.
Paul Hunt

concurr with the above as regards tire age. My car came into my possession with lots of tread, so i daftly thought the tyres were fine. After a whole wet winter of spinning away from junctions and skiting around on corners, I bought a set of alloys and decided to put new tyres on them. What a difference - unbelievable how much more grip i had, and how altogether better the handling has become. When I examined my old tyres they were 18 years old (from my history file) and were very hard - the rubber had just lost its gripiness, and just below the treadline there was numerous cracks. All in all I now consider tyre age to be a major safety factor on all cars i drive.
Mick
mick

Most (not all) Modern tyres have a 4 digit code after the DOT on the side wall. first 2 digits are the week, second 2 are the year of manufacture. Full explanation in MG Enthusiast and Practical Classics recently.
But just look at them! If they look shiney and hard and have hairline cracks where the tread meets the sidewall, they are probably old. As Larry says UV and general exposure are major contributors- a spare kept dry and out of the light may still be good. You have a 4 contact patches about the size of your foot, holding (hopefully) about a ton weight + you to the road.....Not worth the risk really...?M
Michael Beswick

Recently I was hit from the rear in my Mg V8 , the insurance assessor looked at the car and A remarked that the body was very good -apart from the dented rear ! But he also checked all four tyres, as they are brand new -no problem - but if they were old there could be a problem on insurance . None of us look for an accident but ......
Andy
ap lestocq

A few years ago I replaced my standard 165's with new minilites and Pirelli 185/70 tires. The improvement was just great. Much better handling in all cases. Last year I put the old wheels and tires back on because the new ones were getting worn and I wanted to get some life out of the old set. Sure enough the old rostyles with 165's really suck compared to the new set. By the way each wheel/tire combo in the new wheels with 185/70's is 2 pounds lighter than the old set. I can not wait til they are finally worn out so I can trash them. Seeya Bob
Bob Ekstrand

Ap,
That sucks - you get hit from behind, so obviously you had no trouble stopping like the guy behind, and yet the weasels at the insurance company are looking for a way out of coughing up!

When I got my GT it had some Kelly brand tyres on it lots of tread but shiney and rather lairy on a damp roundabout!

Dave.
David Smith

DS you did not realise that about insurers ?
The other side of the coin was that ;as the assessor put it 'why should we pay out for £500 of repairs to an unsafe car !1 Fair point ?
Andy
Ps it was a lady with 3 children in the car- reading between the lines she was distracted by something and bop !
ap lestocq

Someone drove into the side of my GT last year and the first thing the assessor did when he came to inspect my car (and the only mechanical check he did) was to whip out a tread gauge and check the tyres.

As well as the obvious safety impact, I've always looked at the tyres on a car as an indicator of the level of overall care the owner takes of the vehicle. Clearly there are exceptions and that reasoning possibly doesn't hold as well for classics where the correct tyres are less available and the usage is lower - but I think there's a pretty good correlation on modern cars between the type and condition of tyres and the state of the rest of the car (and the interest the owner has in maintenance)! How many moderns do you see with mismatched front and rears, abnormal edge wear, bulging sidewalls from kerbing, etc?

Cheers,
Tim
T Jenner

Matt,
Have you tried adjusting the rear brakes?
Neil
Neil

After some life-threatening situations in the rain I will only use Michelin.
jjralston

Tim

You are right about tyres being an indicator as to owner interest. I see dozens as an MOT tester.... Often the worst have "Baby on board" stickers.... And all the owner has to do is park with the wheels at an angle to see the front and a quick check for the back!. End of rant! FWIW I have 185/70 Yokahama A drive

Michael
Michael Beswick

I do have to wonder if your rear brakes are working right. Maybe a crushed line back there? The wrong diameter wheel cylinders? Worth investigating.
Tom

This thread was discussed between 01/10/2008 and 05/10/2008

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