Opinions on tyre size please

hjworton · Post by **hjworton** » Wed Jan 30, 13 7:06 pm

My newly purchased Roadrunner came with some fairly interesting size tyres fitted - Coopers both front and back(the rubber is degrading, I'm thinking they're quite elderly). Fronts are 215/65/R15 and Rears are 275/60/R15. I've had a search and have a coulple of options on the front, so far cannot find anything in that size on the back. What do we think ? Are these the right sizes ? The rears are huge, I kinda like that. Help !

MilesnMiles · Post by **MilesnMiles** » Wed Jan 30, 13 7:22 pm

Depends how urgent it is. As I have the same car I have to say I like the tyres tucked more under the arches. Irrespective, it's worth knowing that Ford wheels share the same pattern at 4.5 " therefore you may be able to get a tyre/ wheel combination that suits.
Rodsn'sods website is a good place to look for wheels and tyres. New items appear most days of the week.

MilesnMiles · Post by **MilesnMiles** » Wed Jan 30, 13 7:26 pm

Try this thread. 40 pages of 1971/74 B bodies to enjoy and get ideas from.

http://www.forbbodiesonly.com/moparforu ... he-71-74-s

Pete · Post by **Pete** » Wed Jan 30, 13 7:29 pm

You also need to consider your rear gear ratio, as tyre choice can have a big impact on the overall ratio. It could also knock out your speedo accuracy............

Dave81 · Post by **Dave81** » Wed Jan 30, 13 7:33 pm

Not sure you and get Coopers anymore due to the dirty oil wheels or whatever they called are not allowed on british roads!

Possibly BF Goodrich

http://www.northhantstyres.com/RTS%20final/2756015.html

Not used Northants so can't comment!

hjworton · Post by **hjworton** » Wed Jan 30, 13 9:21 pm

Thanks for the answers, Northants tyres look like the best bet. I'll consider all size opinions and options before coughing up. Needs must though, and soon.

RobTwin · Post by **RobTwin** » Thu Jan 31, 13 1:29 pm

I would say 60 series is too short for the rear of a b-body.... 65 at least but 70 series would be my choice

As Pete says, you ought to consider what it will do to your speedo reading. Mind you, it probably isnt right with the 60 series tyres you have

Dave-R · Post by **Dave-R** » Thu Jan 31, 13 1:54 pm

RobTwin wrote:I would say 60 series is too short for the rear of a b-body.... 65 at least but 70 series would be my choice

As Pete says, you ought to consider what it will do to your speedo reading. Mind you, it probably isnt right with the 60 series tyres you have

Depends on the width of the tyre. Obviously the diameter of the tyre increases with width if you keep the same aspect ratio.

I made this handy calculator a few years ago;

http://challenger.mpoli.fi/web/AUTOMATICchart.xls

Enter your tyre size along the top and not only will it give you the diameter, but also (if you add in the axle gears) what speedometer gear you need to keep your speedo accurate.

For best cornering performance you need a tyre that is the same or only slightly wider than the wheel.

Dave-R · Post by **Dave-R** » Thu Jan 31, 13 2:01 pm

Ooops! Sorry. Just realised yours is a MANUAL 3-speed. I only have calculators for the auto and 4-speed. But the wheel size bit will still work for you and if you find out what your manual gear ratios are you can add them in.

hjworton · Post by **hjworton** » Thu Jan 31, 13 5:35 pm

Cheers RobTwin and Dave. Very helpful. Anything that helps the handling a little would be good.

Mick70RR · Post by **Mick70RR** » Thu Jan 31, 13 7:20 pm

I've always used 275/60R15 on the back and 235/60R15 on the front of my Road Runner.
It's getting difficult to find American made tyres over here since the dirty oil law came into effect.
I use these on the back
http://www.tyres-pneus-online.co.uk/car ... H-191.html

I need to find some 235/60's for the front this year.

Mick70RR · Post by **Mick70RR** » Thu Jan 31, 13 7:25 pm

By the way, those Bridgestones are a lot grippier than American tyres like Coopers, and they work well in the wet. The American tyres are designed for their market where people expect to do 50,000 miles on a tyre.

Pete · Post by **Pete** » Thu Jan 31, 13 7:34 pm

£87.95 is a good price!

Mick70RR · Post by **Mick70RR** » Thu Jan 31, 13 8:53 pm

Pete wrote:£87.95 is a good price!

Price seems to fluctuate, I've seen them anywhere between £70 and £100.

I had enough of paying over £500 for a pair of drag radials that only lasted 2000 miles, and were lethal in the wet. I wouldn't mind if these only lasted a few thousand miles at that price but they're lasting a lot longer that I expected despite all the burnouts.

Pete · Post by **Pete** » Thu Jan 31, 13 8:55 pm

Slicks in that big trunk of yours, chap