Another wheel/ tyre question - Sprint on +2rims

[pabbage]

Hey everyone.. I've searched the posts and can't seem to find a simple answer so I was wondering if any clever soul could assist.

Although I've had the sprint for a year I'm still learning its quirks and have noticed its on plus 2 rims with a wider, decade old 185 60 13 tyre with TTR adjustable shocks. Very different from the original set up.

I'd like to revert back to a more 'normal' tyre (Michelin et al) and was wondering what people's thoughts are??

Can I just put an original size tyre on these +2 rims or are they just too wide and would it be a case of new rims too?

Currently there doesn't appear to be any issues with rubbing of fouling with the current rim and tyre size but if I kept a slightly wider tyre with a slightly higher profile (175 70 13) would I then get into some issue with clearance?

Thanks in advance as always!

[MarkDa]

The +2 rims will be a bit wide for 155 section tyres - optimum width is 4.5" - but they will go on.
If 185 width don't rub then 175 won't.
175/70 is same overall height as 155/80 so gearing will be right and a good fit on +2 rims.
In round terms new standard rims and Michelin tyres will cost about ?2k in total.
You may well find that new 175/70 tyres will provide better grip than your tired rubber and better ride quality.
Certainly would be a cheap option to try.

[1owner69Elan]

The problem with the 175/70 vs 185/60 is that the 175?s while narrower are taller. The 175's are close to the original 155's in diameter so that appears to be OK but they are also wider than the 155's.

The net effect is that while the 175/70's may not rub in normal use on an S4/Sprint they can foul the top of the front arch on full lock and bounce. Like turning into a driveway that has a dip.

Since you have TTR adjustable shocks perhaps you also have stiffer front springs that would help mitigate the travel on full bounce. That might save you, but if the dip is severe enough to initiate full bounce then you can see below what can happen,. Real life experience:

175/70 r 13 on an S4 with stock springs, at full lock and bounce. Both front arches had similar damage from separate occurrences.

I now have 185/60's on 26r wheels with stiffer springs and have no arch rubbing problems as above. I should note however that I had to increase the rack limiters to keep the tires from fouling the ARB on full lock. Trade-offs and unintended consequences when you stray from stock.

In my case quite happy to have the wider rubber to handle increased hp in conjunction with a properly sorted, uprated suspension.

[pabbage]

Thanks for both the replies - really interesting stuff. And the damage you have suffered on the car was something I was concerned about through reading other posts. I've definitely not had any scuffing or rubbing during my use though I can't think of a full lock bouncing incident.

Funnily enough I had a reply from a well known tyre place in the UK - they recommended Pirelli CN36 175 70 13

A couple of questions on the back of this:

1. At what point in BHP improvement do you feel there's a need for more rubber? Is there really a need for wider rubber under 150bhp?

2. Would a 175 tyre fit as a spare? Currently the 185 60 in my boot means the boot floor does not sit flush - which really annoys me!

[MarkDa]

I have to admit to having caught a wheel arch many years ago when I put 165-13 tyres on - I think because they had H rating.
It was just as described- a lot of lock turning up over footpath into my drive.
Not as bad as picture but I took them off!
I have fond memories of CN36 tyres on my 1.6 Escort and then Dolomite Sprint in the 80s - a very nice tyre.
So it sounds as if it would be prudent to get a tyre and check clearance with springs removed to be absolutely sure.
Even tyres of same nominal size have slightly different widths and shapes at the tread. I seem to recollect that CN36 is quite rounded unlike more modern tyres designed for lower roll cars.