Changing wheels and tyres

[Tyre Tread]

My car is currently fitted with 185 80 15 tyres on 5.5j rims

I have a new set of wheels for the car which are 15 inch 6.5j.

I want to keep the tyre width as low as possible on the new rims and keep the rolling radius as close to original as possible so what are the narrowest tyres I can put on 6.5" rims and what aspect ration will I need to keep the rolling radius as close as possible to original?

Advice appreciated please.

[iva cosworth]

Tyre calculator here

http://www.etyres.co.uk/tyre-size-calculator.htm

I was going to suggest 195/70 15 but maybe too low profile.

Using the above site 195/75 is close but i have never heard of 75 as a profile.

[Tyre Tread]

Thanks Iva. I was using a tyre calculator but am more worried about hwat if the minimum width I ca n get away with on a 6.5" rim

[na]

185/80/15 tyres will fit 6.5J wheels but compared to 5.5J wheels this could give a harsher ride because the sidewalls will not have the same curvature to make them flex as much over bumps and potholes

215/70/15 would be a good tyre size as it will fit the 6.5J rim better and will only give a 0.74% increase in circumference - so that at 70 mph on an accurate speedo your actual road speed is 70.52 mph

I know you will want to confirm this and work it out for yourself so here are the links –

http://www.carbibles.com/tyre_bible_pg4.html

http://www.yokohamatire.com/tires_101/customizing/...

http://www.yokohamatire.com/tires_101/customizing/...

[TheInternet]

na said:

185/80/15 tyres will fit 6.5J wheels

It's that simple, and you already have some (boon).

[na]

that depends of course on how old and unused those tyres are, I sure they'll be fairly recent and fresh

[Tyre Tread]

Nigel, if you remember you have already made those disparaging and sarcastic remarks and I told you that the original tyres from the 'new rims' were ditched as they showed signs of cracking and were clearly old and unsafe.

The tyres I already have are on the car, are ALL less than 10 yeras old but I do not intend to use them on the 'new' rims. If you recall, you and I looked at the tyres on the Rover together not too long ago and checked the manufacture dates

Happy now?

[na]

you flatter yourself the remark wasn't aimed at you it was a reply to TheInternet and a general remark about the subject

and your memory is going it wasn't me you checked the tyre dates with or I wouldn't have thought you'd got recent tyres, and by recent I don't mean 10 years ago

[Tyre Tread]

na said:

you flatter yourself the remark wasn't aimed at you it was a reply to TheInternet and a general remark about the subject

and your memory is going it wasn't me you checked the tyre dates with or I wouldn't have thought you'd got recent tyres, and by recent I don't mean 10 years ago

T'was you who was kneeling on my garage floor looking for the dates on the tyres!

[na]

Tyre Tread said:

T'was you who was kneeling on my garage floor looking for the dates on the tyres!

can't remember that, how many years ago was that, if I did I couldn't have found a date or I would remember

anyway if you're getting new tyres they will have a manufacturer's approved rim width range possibly with a prefered size in the middle of the range

[SonicShadow]

They make 80 profile tyres? TIL.

[Tyre Tread]

SonicShadow said:

They make 80 profile tyres? TIL.

yes but they becoming increasingly difficult to get hold of in anything other than 8 ply van tyres which makes the ride hard and uncompliant.

[biffonracing]

You havn't said what sort of car or era it's for, but both the people may be able to help and even if they can't I'd imagine they will know who can


http://www.longstonetyres.co.uk/

&

http://www.blockleytyre.com

[Tyre Tread]

biffonracing said:

You havn't said what sort of car or era it's for, but both the people may be able to help and even if they can't I'd imagine they will know who can


http://www.longstonetyres.co.uk/

&

http://www.blockleytyre.com

I didn't say because I didn't want the thread to deteriorate into a 'That will look crap' or 'Have you considered you'll need different wheel nuts' kind of thread.

Since you asked I am putting GKN Alloys as fitted to Jenson Interceptors to a Rover P5B.

I always think they are the wheels tha car should always have had. The stud pattern and offset is the same and I have sourced a fairly decent set of wheels and had wheel nuts made to suit (different seating on the Rover wheels (tapered) Vs the Jensen (flat)).

Both are 15" but I've always run the Rover (12 years) on standard 185 X 80 X 15" tyres but as the Jebsen rims are 6.5J v the Roverv 5.5" I didn't know if they'd fit and whether there will be isuues with clearance.

Now let's see what can of worms that info opens.

Incidentally I don't want the tyres any wider then necessary as it placed additional strain on the suspension joints.

[Whitefly Swatter]

Tyre Tread said:

Now let's see what can of worms that info opens.

Incidentally I don't want the tyres any wider then necessary

Keep air in them I have found this helps !!!!!

[Dougal Cawley]

http://www.longstonetyres.co.uk/page/Vintage-Tyres

on this page the "search for your vintage tyres by rim their rim diameter" drop down list offers you rim sizes. if you choose 15" rims it will then show you all the 15" tyres in ascending order of the overal diameter, while at the same time giving you all the other dimentions of the tyres as well.

[na]

those prices will give T-T a heart attack

Dougal,
you might also appreciate these links
http://www.carbibles.com/tyre_bible.html
and
http://www.carbibles.com/tyre_bible_pg4.html

[Tyre Tread]

na said:

those prices will give T-T a heart attack

Dougal,
you might also appreciate these links
http://www.carbibles.com/tyre_bible.html
and
http://www.carbibles.com/tyre_bible_pg4.html

Nah. Longstone are known for their 'niche maket tyres' being pricey.

I have a source of 4 185 X 80 x 15 (not commecial) tyres the same as already on the back of the Rover brand new at £280.00 inc VAT delivered. I'm assured they are not old stock and am just waiting for confirmation.

Since Nigel assures me they'll fit OK on the wider rims I'll take the cost out of his paintwork (after the respray) if they don't fit well on the 6.5j rims

[na]

respray is off again for a while as engine and gearbox are coming out (again)

if you're not going to be using it soon I might need to 'borrow' some coolant as the firm that does it have stopped after 20 years and the new lot are still doing the label despite the time of year and it being on promotion so no stock - it's amazing the lengths some will got to to foul me

[na]

na said:

185/80/15 tyres will fit 6.5J wheels but compared to 5.5J wheels this could give a harsher ride because the sidewalls will not have the same curvature to make them flex as much over bumps and potholes

and it's not even in small print

four, what about puntures