911 ST Wheel and Tyres sizes

[rich73]

I ordered 285/50/15's and was surprised by how much sidewall there is.

Is it just me that didn't know until now that the sidewall measurement is a percentage of tire width?

[BILLY BEAN]

I ordered 285/50/15's and was surprised by how much sidewall there is.

Is it just me that didn't know until now that the sidewall measurement is a percentage of tire width?

In answer to your question. Probably. Sometimes refered to as the aspect ratio. Once on the car they will look fine.

[Lightweight_911]

I ordered 285/50/15's and was surprised by how much sidewall there is.

Are you sure they're not 285/40/15 ?

.

[rich73]

Hi There,
Yes checked and they are 285/50/15. I’ve been doing lots of measuring to try and determine if the tyres will fit under the arches . I’ve also rerouted the oil lines to get them out of the way.
I’ve not actually fitted the tyres to the rims as I wont be able to swap the tyres once they are fitted if they turn out not to have enough clearance.

I’d be really grateful for anyone thoughts on where I go with this. To summarise:

Wheels
Rear 9J x 15 ET3
Front 7J x 15 ET 23,3

Tyres PIRELLI CINTURATO P7
Rear 285/50/15
Overall inflated diameter 666mm / Width 288mm / Recommended rim width 8.0” to 10.0”
Front 225/50/15
Overall inflated diameter 608mm / Width 229mm / Recommended rim width 6.0” to 8.0”

I’ve fitted the wheels to the car without tyres to check the offsets.

20240714_130055 by richard cannings, on Flickr

Front offset looks good. With camber at mid point, Inside arch to rim is 25mm, outside 50mm overall 275mm
Rear offset looks good, Inside arch to rim 35mm, outside 25mm overall 295mm

20240714_132136 by richard cannings, on Flickr
20240714_132322 by richard cannings, on Flickr

To get a better idea of tyre clearance I’ve held the rear one up to the arch. (Only did rear as fronts look fine).
Firstly to me there definably looks to be too much sidewall , this is backed up overall diameter of 666mm compared 608mm for the front.

20240715_104111 by richard cannings, on Flickr

In terms of tire clearance width ,I’ve measured the tyre width un inflated at its widest point as 288mm (same as inflated specification). With the tyre touching the inner arch I’ve measured 10mm on the outside. i.e. 5mm each side. This could be increased another 5mm if I rolled the arches.

My thoughts so far.
• Front look fine for clearance and there are no issues there.
• 285/50/15 on the rear with a diameter of 666mm is too much sidewall.
• 285 width looks like it would fit but only just and I suspect I would have to adjust the camber to get the tyre to clear rather than be able set it to where it should ideally be.

Options
1. Go with 285/40/15 on the rear, this would give overall diameter of 609mm . I think this would look better but width is still 288mm so clearance is tight. Also recommended rim width for this is listed as 9.5 – 11”. Not sure why.
I have the risk here if it doesn’t clear I end up with tyres that I can’t return.

2. Next width down for Cintiurato P7 is 225/50/15. This is what I currently have for the front. Holding them next to the rear rims it looks like this may be an option for the rear but the recommended rim with is 6” to 8”. Thoughts on this welcome?

20240714_123545 by richard cannings, on Flickr


3. Accept that although Cinterato P7 is really the ideal tyre for my use I go with TB 15 as I’m confident they will fit, rear width of them is 270mm giving me an extra 18mm of clearance. Also Kirk has the same arches on his car as I do and I’m presuming his TB15’s are 270

I’d be really grateful of anyone’s thoughts as I really want the car on the road in the next few weeks but really not sure where to go with this .

[RobFrost]

All I have to say is;
a) have you rolled the lip over on the arches? Likely is necessary I would have thought.
b) maybe it's ok if they rub a touch on cornering? That's up to you I guess but this is a race car
c) camber will buy you more room at the arches, at the expense of less clearance on the inner arch, so consider your camber setting.
d) does camber change with deflection? If so, you may have more room than your think.

[IanM]

Options
1. Go with 285/40/15 on the rear, this would give overall diameter of 609mm . I think this would look better but width is still 288mm so clearance is tight. Also recommended rim width for this is listed as 9.5 – 11”. Not sure why.
I have the risk here if it doesn’t clear I end up with tyres that I can’t return.

Have you thought about swapping your wheels for 16" diameter? That way you can use 930 Turbo tyres (rears 245/45/16). Available in Pirelli P7 and Michelin SX MXX3 (N2).

[rich73]

Thanks for your thoughts,
I've run lot of camber on my 3.2 before to get clearance so probably need not worry too much about that. More worrid about:

images (7) by richard cannings, on Flickr

I'm really keen to try and keep on 15" but thanks for suggesting 16", I think this may be a good backup plan.

Current thinking is give the 285/40/15 a try, Longstone have said they would exchange the 285/50/15 for these. I mount all the tyres tand give it a go.
If they don't work then sell the 15's with tyres and buy a set of 16's. The 15's are currently out of stock with Rose Passion and 16's are in stock so might be able to get a decent price for the 15's.

Rich

[IanM]

More worrid about:

yellow ST replica.jpg

[Dougal Cawley]

Hi There,
Yes checked and they are 285/50/15. I’ve been doing lots of measuring to try and determine if the tyres will fit under the arches . I’ve also rerouted the oil lines to get them out of the way.
I’ve not actually fitted the tyres to the rims as I wont be able to swap the tyres once they are fitted if they turn out not to have enough clearance.

I’d be really grateful for anyone thoughts on where I go with this. To summarise:

Wheels
Rear 9J x 15 ET3
Front 7J x 15 ET 23,3

Tyres PIRELLI CINTURATO P7
Rear 285/50/15
Overall inflated diameter 666mm / Width 288mm / Recommended rim width 8.0” to 10.0”
Front 225/50/15
Overall inflated diameter 608mm / Width 229mm / Recommended rim width 6.0” to 8.0”

I’ve fitted the wheels to the car without tyres to check the offsets.

20240714_130055 by richard cannings, on Flickr

Front offset looks good. With camber at mid point, Inside arch to rim is 25mm, outside 50mm overall 275mm
Rear offset looks good, Inside arch to rim 35mm, outside 25mm overall 295mm

20240714_132136 by richard cannings, on Flickr
20240714_132322 by richard cannings, on Flickr

To get a better idea of tyre clearance I’ve held the rear one up to the arch. (Only did rear as fronts look fine).
Firstly to me there definably looks to be too much sidewall , this is backed up overall diameter of 666mm compared 608mm for the front.

20240715_104111 by richard cannings, on Flickr

In terms of tire clearance width ,I’ve measured the tyre width un inflated at its widest point as 288mm (same as inflated specification). With the tyre touching the inner arch I’ve measured 10mm on the outside. i.e. 5mm each side. This could be increased another 5mm if I rolled the arches.

My thoughts so far.
• Front look fine for clearance and there are no issues there.
• 285/50/15 on the rear with a diameter of 666mm is too much sidewall.
• 285 width looks like it would fit but only just and I suspect I would have to adjust the camber to get the tyre to clear rather than be able set it to where it should ideally be.

Options
1. Go with 285/40/15 on the rear, this would give overall diameter of 609mm . I think this would look better but width is still 288mm so clearance is tight. Also recommended rim width for this is listed as 9.5 – 11”. Not sure why.
I have the risk here if it doesn’t clear I end up with tyres that I can’t return.

2. Next width down for Cintiurato P7 is 225/50/15. This is what I currently have for the front. Holding them next to the rear rims it looks like this may be an option for the rear but the recommended rim with is 6” to 8”. Thoughts on this welcome?

20240714_123545 by richard cannings, on Flickr


3. Accept that although Cinterato P7 is really the ideal tyre for my use I go with TB 15 as I’m confident they will fit, rear width of them is 270mm giving me an extra 18mm of clearance. Also Kirk has the same arches on his car as I do and I’m presuming his TB15’s are 270

I’d be really grateful of anyone’s thoughts as I really want the car on the road in the next few weeks but really not sure where to go with this .

Ouch! / Woops!

Put your tape measure away and stop faffing around. just ring us up and we will sort it out as long as you havent driven on them.

What you want is the 285/40R15 P7

https://www.longstonetyres.co.uk/catalo ... gory/6932/

the ones you have are the rear tyres for a DeTomato Pantooney. very different. it should have 10% of 285mm extra radius. that is going to make things awkward.

Ring Longstone. We don't like to let our customers down. (that is assuming you got them from us?)

[rich73]

Thanks Dougal,
That's just what I did at the end of last week and Simon at Longstone was amazing. Collection and drop off arranged next day without drama and I even ended up with a refund for the price difference.
Amazing service thanks. The 285/40/15's are defiantly what I needed . There might be a bit or arch rolling needed when things are set up properly but up and running which is great.

20240719_105859 by richard cannings, on Flickr

20240723_134919 by richard cannings, on Flickr

20240723_134618 by richard cannings, on Flickr

[matteo68]

Looking beautifully orange Rich!

[Dougal Cawley]

Thanks Dougal,
That's just what I did at the end of last week and Simon at Longstone was amazing. Collection and drop off arranged next day without drama and I even ended up with a refund for the price difference.
Amazing service thanks. The 285/40/15's are defiantly what I needed . There might be a bit or arch rolling needed when things are set up properly but up and running which is great.

20240719_105859 by richard cannings, on Flickr

20240723_134919 by richard cannings, on Flickr

20240723_134618 by richard cannings, on Flickr

Phew!

I'm glad we sorted it out for you. We don't like to leave our customers in the lurch. That Simon is also a fine chap. I've known him for ever. He went to shcool with my wife and i think he has been with us here for about 25 years. And he was a certified petrol head before that. Both our first cars were Beetles.

[Dougal Cawley]

That is great news. this post has just really helped a customer finalise his decision as to wht tyres to fit on his ST. he has also gon for the p7 225/50R15 and 285/40R15 P7 on 8" and 9"

[Magnum]

Uhhhh, oooops

Apologies in advance, but don't those look a little low profile, a bit like a well-used rubber band or is there absolutely no alternative these days?

Sorry for the honesty, hope it's misplaced....

[sladey]

Ok so I’ve got the 225/50 on the rear of mine. Not particularly rubber-bandy