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MG MGB GT V8 Factory Originals Technical - Tyres, technical question!

There's much comment in the archives that a 60 series tyre is really as low as you can really go to retain a decent ride. Am I right in thinking that this applies to all 60 series tyres or is it more a question of the height of the actual sidewalls? i.e. a 205/55 tyre has a taller sidewall than a 185/60 and does this therefore make it more comfortable?

I only ask because my 185/60/14 Yokohama A509s are several years old and no longer perform properly. I'm considering a switch to 195/60/15s or 195/55/15s (I would like some Toyo T1-S). My axle is fairly central and the tyres should therefore fit ok both sides but I'll be trying one for size just in case. If anyone has any experience of these tyres I would be grateful for any comments.

Thanks, David.

David Canning

"to retain a decent ride" - you might need to consider the suspension and road conditions as much as choice of tyre.

A couple of thoughts:

the choice of bushes, panhard rod etc, will affect sideways movement and therefore whether broader tyres will rub on the inner wheel arches. Even if the tyres do not touch, 195s will drag round debris which will strip off the paint.

The ride with 195/55 X 15 is markedly harsher than 185/60 X 14. (You will recall the factory car was fitted with 175s.)

Yes there are variations between makes - some tread patterns simply don't feel right - as you say; there are size variations.

I use the OE V8 wheels with 185s in the Summer and 195/55 on 15" SAAB wheels in Winter - the car is pretty well glued to the road on the 15" but it is always nice to get back to the OE kit.

There will be other views !
RMW

David,

The 15s give a noticeably harder ride, but depends on your preference as a ZS also gives a hard ride.

Interesting to find out what the 17in RV8 wheels are like in this respect.

I use Eagle F1 with 195x60x15 but Toyo's have a good reputation with the F's.

Paul
Paul

I have fitted Compomotive ML 6"x15 ET6, Yokohama ADVAN 032R 195/55x15 I have also fitted Nylatron bushes and Panhard rod, no problems with the lips in the wings.
Regards.
http://membres.lycos.fr/mgcontact/fileupload/uploads/tyres.jpg
michel

Michel

ET6 would push wheels closer to lip, do you have a w/w axle?

Paul
Paul

Paul,
I don't know. My rear axle is a puzzle. I have axle with short drive shaft (Jack Knight origin).
Regards.
michel

Michel,

Has is some racing pedigree

Paul
Paul

Paul,
I have built this car with a "racing" spirit. Not for daily use, rather track day. Handcraft is my pleasure, the car don't run a lot, but it is a very, very good car. Now I built ally doors skin and ally boot lid skin. The MGB boot lid is very heavy. All handcraft make, it's an interesting job.
At the planning stage, a Mini, a true Mini, 1969. My true passion is the Mini, but I have BGT for daily use!
Regards.
michel

To answer your original tyre question, the sidewall stiffness of 60 series or any other tyre will vary considerably depending on their intended application.
Higher speed ratings imply higher performance aspirations and so a stiffer sidewall to improve steering precision.
I can sit on an unmounted 205/50 15 Z rated tyre and the sidewall will support my weight (200lbs.)
A luxury car tyre or general application design is much softer.
Simon.
dominic clancy

I just refinished a set of Carroll Shelby Saab 900 Turbo minilite type wheels for my 1980 B. I finally decided on 195/60/15's after seriously considering 205/60/15's maybe i will try that size on the 78 B. The tires ride well with no rubbing. The wheels are 15x5.5 inchers.
Alex

The tire aspec is important for a good quality ride, yes, but with that goes the little number on side wall of the tire, which reads; TREAD WEAR 50,300 or nothing. what this numbers mean, is how sticky the tire is. A Z rated tire could be a T W 200 or 50
A 50 TW tire would not last on the street very long a road racing DOT street legal tire usally are 50 to 100 some racing classes require DOT street legal tires.
When you combine these tires with a tire aspect of 50 and TW of 100 it will make the car lean more than normal do to the increase of traction, meaning reduce slip angle, thus requiring stiffer springs with match shocks. For a good ride choose a tire with TW 200 with a tire aspec of 55 or 60 and the aspec will differ between manufactures, the aspec ratios are just guidelines, meaning that a Goodyear tire 225X50X15 TW 200 compare to a BG of the same size, the sidewall would be different thus given different ride quality.
Also the construction of a lower TW number will have stiffer sidewalls (in some cases)
What makes a tire sticky is the quantity of resin that is induce into the tire at time of construction, more resing softer compound lower TW # stiffer sidewall.
The reason for stiffer sidewall is to reduce the slip angle with the increase traction. Everything is balance.
Bill Guzman

Alex, I've just acquired a set of the same Shelby/SAAB 5 1/2" x 15" wheels. I haven't even found time to trial fit them on the car ('73 'B) yet.

Are Yours marked ET40? You say there's no rubbing. Have you lowered the suspension to CB height or are you still at the standard RB height? Which brand & model tire are you using? What did you use for lugnuts and where did you get them? I read in the archives that the SAAB is (not surprisingly) metric. Did you check that the standard studs are long enough? Sorry about so many questions, but I'm trying to save myself from any problems.
Derek Nicholson

ET40 will use space at rear inner but may give interference at front, as well as reducing track width.
Slip angle relates to footprint deforming, the wider the tyre the less the footprint can deform.

Michel,

A Jack Knight halfshaft implies its been uprated in a previous life, re the rear axle puzzle.

Paul
Paul

Derek, my Shelby wheels have E40 on them. My 80 B has been lowered slightly. It's at about the height of my 73 B's original ride height which was lowered even further with 3/4 de-arched springs and lowered coils up front. The 78 is the fed height. I'm using Sumitomo HTR 200's. Real nice looking tire that sets the B off. I wanted to try a different tire, usually a Yokohama man on the SUV's. I'm using the "Lug Master" mag kit with 4 locks and one key. 1/2" R.H. standard mag kit part number 711-248. The mag kit is manufactured by Dorman and available from O'Reilly's. I kept the standard MGB studs.
Alex

This thread was discussed between 28/04/2004 and 09/05/2004

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