73T tyres!

[911hillclimber]

Thank you for the advice!
John (long time friend and new fellow DDK'r) dropped off two of his rally car wheels off the front of his 73T on 6" fiche this morning.
They are 185 Blockley tyres.
I'll fit these tomorrow and take the car for a drive to see if the wobble is the same as it currently is.
Today, my wheels are behaving themselves.
Hope to feel a steering difference with 6" on the front and 7" on the rear.
It will be interesting to test.

If it is much better then I only need one 6" cookie and correct tyres and the car could be sweeter still.

You must all remember, I don't blast around this car anymore, just simply drive it on high days.
It was very different to its hill climb days, but I don't fool around on the public roads, so ultimate grip etc are of little relevance.
I've got a real race car for all that stuff.

Lighter steering would be nice as it is a bit wooden until 30 mph, but that must be geo more than tyre construction.
It drives very confidently as it is, and so far the wobble has gone.

As to the pictures, the crazy balance weights and the localised tyre run out I hope explain the wobble?

[Winston Teague]

I have an On the Car wheel balancer, it is fantastic at seeking out wobble. You are welcome to come over and have a go.....W

[911hillclimber]

Thank you Winston, you are close to me so may well take you up on that!
Do you fix magneto coils too!?

Well, did the wheel-swop test this morning while the sun was shining.

Just to re-cap:
The car on it's 7" cookies is running ok at the 65/75 zone now I've swopped the fronts around and seem to have found a combination that has smoothed the wobbles.
It is now difficult to separate wheel 'out of balance' wobble from general road surface vibration such is the 911's steering feel we all love.

John delivered 2 of his rally car wheels yesterday before we went off to the Morgan Factory Visit (bloody great it was too) so after washing all the quarry dust off I replaced the front 7" with these 2 x Fuche 6" with 185 Blockley tyres.
John is as sensitive about car handling as the 911 steering is and he loves this combo.

28 psi pressures and off we went to find the M54 that is billiard table smooth by Shrewsbury and open enough to hover ar 65/70/7*/** mph so any wobbles will have time to manifest themselves or show a cyclic rhythm that is tyre in-balance.

A number of observations, 6" front/ 7" rear:
1 The steering wheel is no long horizontal! On the 7" fronts it is. That was a surprise. It would be a spline 'out'.
2 the steering has a 'normal' vibration at all the above speeds, there is a fine consistent vibration but I think this is 'old 911' typical. (I'm so used to modern power steering like we all are)
3 It drives SO MUCH nicer, arrow straight as ever, but all the familiar bends of the area I've driven for 40 years are so much lighter and relaxed.
4 Braking is unaffected, no better, no worse on normal driving brakes, no panic stops, they are not my tyres!
6 Understandably, the Fuch are much lighter than the 7" cookies, very noticeable when changing the tyres.
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So, what now?
I drive this car maybe 1000 miles/1500 a year, is it worth swopping the wheels to Fuche?
Is it worth swopping the tyres to Blockley's?
Is it worth changing the fronts to 6" Cookies and Blockley's all round or AVON ZT7's?

Time for thought.

Many thanks to old friend John for the loan of the wheels! I'll get them back asap after you know what John this week.

[hot66]

it looks better on the 6" too

Personally don't think there is any need to run 7" up front on a normal bodied road going early 911

[911hillclimber]

Coming to the same conclusion.
I used the 7" all round because of the hill climb tyres I could get that were grippy.
Car was great on track.

I have a lone 6" cookie that was the spare with the car when I bought it in 89. The car was on 6" cookies all round when I got it.
I had them refurbished in silver and G800 Goodyear 70 section tyres fitted and it drove a dream once Bob Watson had set the suspension up in 1990.

In fact I called Bob up after getting home after my first 911 drive and said I thought the steering was wrong, it was so light and wriggled about (I had an MGB GT before).
He laughed and said it was normal....

I think I will find another 6" Cookie and get both re painted in the same colour as the current 7" and then think about tyre choice.

Oddly, those Blockley's sure look like Goodyear G800's which you can still buy.

[Dougal Cawley]

I think i have the problem:

do you have any balance weights on the outside of the wheel?

Modern wheel balancing wheels offer that opportunity to just do the balancing on the inside bead seat. This is flawed! specially when you have a wide outer bead seat, like on your car.

balance the wheels again putting your weights on the very inside of the flange and the very outside of the rim (not inside the spokes) you will find this fixes your problem of vibration.

if you cannnot bare to have the balance weights visible on the inside of your rim, you may be able to get away with static balancing, (not dynamic. just one weight in the centre of the rim). Or take all your weights off and go see Winston.

The best way to get this done professionally is go see Wobbley Steve https://vibrationfree.co.uk

I only have a CSE grade 4 in English so i have drawn a picture to demonstate. i didn't take art at school so there is no numirical score as to how rubbish my pictures are.

Hmm struggled getting it up. try this link https://scontent-lht6-1.xx.fbcdn.net/v/ ... e=5DFAF9CD

[Dougal Cawley]

Does this work

[911hillclimber]

Thank you Doug for taking the time to show-off your other skills!

All 5 wheels (the 7" Cookies and the Dunlop Blu Sports) have a huge number of weights all over the place round the 'Diagram 3' of your sketches.
The amount of weighting is not good to the 'engineer's' eye so to speak.
The Kumho tyres on before had about 50mm of them on the inside outer bead edge, that is all.
The huge Bridgestone N rated tyres on the rear of my Boxster (19" wheels) needed NO weights to get 'Zero' out-of-balance and it is vibration free. The fitter was surprised!

It was this weighting of the Dunlops that made me think I had a bad batch (all 5 bought together from a big retailer). Surely a modern tyre today should be really well balanced.
Blockley claim to balance each tyre off the rim before sale, not sure if that implies some are not too good …

Going off for a drive at all normal for me speeds this afternoon and will see how they compare to when the Blockley/Fuch wheels were on.
Tempted to strip the weights off the two fronts and take them to my local small fitting shop for a balance.
The weights fitted now were placed by the shop that reburfished the wheels and re-fitted the Dunlops. The fitter was about 14 years old, my local man is 114 years old.

Here is a picture of the tyre now seconded to the Spare Tyre, the weights are covered by a think high adhesive aluminium tape.

[911hillclimber]

So, back from my usual road test on the M54 billiard table of a road by me, and the wheel wobble, now a vibration, is possible less 'severe' than when I had the Blockley/fuch 6" rims on the other day, certainly no worse.

However, with the 6" rims the steering wheel noticeable was out of true, one spline at a guess compared to the horizontal wheel position with the 7" rims on.

This must be due to geo differences and forces induced by the wider rim and tyre shape.

Still, it drives nicely, does not make my hand go numb on a good journey, so will stay this way until I've used the tyres more, not spending more money on cars for a while.
Will probably do a fresh re-balance bearing in mind what Dougie has proposed now he has planted the seed!

[Dougal Cawley]

The balance on that wheel is Wrong. I mean really bad.

Tke all those weights off and have them Static balanced. (ie in just one place) or have balance weights on the outer flange.

Throw away 14 year old tyres.

Quality tyres https://www.longstonetyres.co.uk/tyres/ ... 36-n4.html or of course https://www.longstonetyres.co.uk/tyres/ ... n-xwx.html will be much better balanced. the amout of weight we put on these is less than a budget brand. (that doesn't count if your wheel isn't perfect. you can't polish a turd)

However you have got wrong size tyres on it. just buy the good stuff. it costs a bit more when you buy them, but they are on there for a long time, so just suck it up. (oo that was a bit brutal, sorry, but i have just come back from the pub)

Be careful with what wild claims budget tyres make about there tyres. At the bottom of this web page https://www.longstonetyres.co.uk/classi ... tml#page=6 there is an article that might put an alternative, independent view against some of things you are being told by people trying to sell you budget tyres.

Yep i sell all brands of genuine classic tyres. Yes i now refuse to sell Blockley tyres. yes i do sell Michelin and Pirelli. yes they are more expensive. However lets look at it objectively. It isn't just me that says Michelin and Pirelli that make the worlds best tyres. They are the only ones that sell proper, genuine, period tyres. the only other competitor in my mind is the Avon CR6ZZ. which though it isn't a period tyre it is designed to go on cars of this period so it does hanndle very well. But doesn't look right and has a race compound.

Please do scour any Porsche forum you like and please do let me know if you can find anyone that has fallen for my sales pitch and is not over the moon with the CN36. in fact don't stop at Porsche. find someone that doesn't like the CN36

[Dougal Cawley]

Er

Prop Shaft out of balance ????????????

[Lightweight_911]

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911 = rear engine/rear wheel drive (no propshaft) ...

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[Dougal Cawley]

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911 = rear engine/rear wheel drive (no propshaft) ...

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Only Joking

[911hillclimber]

I hear you Dougie!
The tyres are 3 years and maybe 2500 miles old.
Bought them for wet weather rating and low noise.
At the time the rolling dia was close to the 3.2 Carreras rear tyres so for once the speedo shows the right,ish speed.

Current rims are 7" so 195 is good for the width, 65 profile gives the diameter.
Not sure why this size is wrong.
Factory fitment is close to this.
For 25 years I drove the car on 205 x 50 and it was really good but not quite the classic car look.

I don't dive sideways on public roads, tend to keep to the speed limits.
I have a real race car if I have a performance itch to scratch, so on the limit grip etc is not high on my list.
Those fab CN tyres are about £1000 for the car, Dunlops were 200 so quite a difference, but balance should not be an issue with either, despite the price difference.

I have had 3 sets of these Dunlops on my tow car, 2014 Skoda Superb, albeit a different size but same tyre.

Perfect running balance every time.

Final for now, when these wheels had the 50 profile Kumho V70 on, 2 sets, they needed almost no weights to balance, so I am presuming the rims are true.

[Gasoline]

That Dougal fellow; in the matter of automotive rubber, his word is the truth!

His advice resolved my wheel wobbling woes.