Tyre choices

[AlanT]

Hi All,

still got a slight rub on my Spit 1500, inner top of arches on big bumps. Arches are lightly rolled already. 175/70/13 on Cobra Super Slots. All is well with rears. Before I ditch these lovely wheels in favour of 5J standard rims (think I’ve found some to swap tyres onto) I wonder if there is a slightly narrower tyre that won’t mess up the gearing/speedo? 
Thanks

Alan

[Clive]

All sorts, depends how much less width you need. And remember, 10mm narrower (ie 165 width) will only give 5mm extra clearance on the outside. 

So 165/70 13. or even 155 80 13 (orginal Spitfire size, and they work better than people expect)

the 165/70 are slightly smaller diameter, so speedo will overread about 5%. Your current tyres have the same diameter as the original 155 80 13.

[AlanT]

Thanks @clive Will 155/80/13 be too narrow for a 5.5 rim? It would solve the problem but I don’t want to cause another! Thanks Alan

[Clive]

I have had thenm in the past, even an Astra (good lord, that was 27 years ago) had factory 5.5x13 wheels and 155 tyres. 

Remember 5.5 rim is about 140mm wide, so the sidewalls will be pretty parallel. a 185/60 tyre on a 5.5 is as wide as I would use, it "balloons" enough, more would become unstable.

But ultimately, do some checks. It seems most charts suggest 165 is as narrow as you can fit, but the 80 profile will help. (very few tyres are 80 profile, so they get ignored by most websites)

[AlanT]

@clivethanks. It seems that it’s standard fit on trailer wheels https://www.trailertek.com/trailer-parts/155-r13-c-8-ply-4-on-5-5-pcd-wheel-assembly?gclid=CjwKCAjw46CVBhB1EiwAgy6M4p9ercGxIqbALR175vmPyQ7yHGoBoB2ZgauOx49sCyIsUpJrZqriMBoCYFcQAvD_BwE

Would love to hear any opinions from others who may have travelled this path, before I splurge more scarce funds! Thanks 

[Stratton Jimmer]

My (Originally a Spitfire 1500) Sixfire has 175/70/R13 all round which hold the road incredibly well but are probably a little too large. My Mk3 GT6 has 155/80/R13 on the front and 165/80/R13 on the rear. The steering is very positive and I will most likely go for 155/80/R13 all round when the rears come up for replacement. When I had my Mk1 GT6 back in the late 70s / early 80s, it came to me with 165/70/R13s on and I changed them for 155/70/R13 which improved the handling immensely.

[AlanT]

@Stratton Jimmerthanks. What size rims? My query is can I use 155s on 5.5 rims. Seeing if others have. 

[Stratton Jimmer]

5J 13 Minilites.

[johny]

According to the wonderful internet the minimum recommended tyre width for 5.5 rim is 165

[AlanT]

I’ve seen this as well @johny yet trailer tyres are all 155/80 on 5.5 rims. 

[johny]

you have to see what your insurer thinks....

[PeteH]

I would be wary of taking trailer use as a yardstick. The forces applied will not be the same as when used (especially) of the front of a car, no steering forces for one.?

Pete

[1969Mk3Spitfire]

17 hours ago, AlanT said:

@Stratton Jimmerthanks. What size rims? My query is can I use 155s on 5.5 rims. Seeing if others have. 

According to the European Tyre and Rim Technical Organisation, ETRTO, handbook, 5.5 inch rims are not recommended for 155/80 section tyres.

[Colin Lindsay]

On 14/06/2022 at 13:57, AlanT said:

@clivethanks. It seems that it’s standard fit on trailer wheels https://www.trailertek.com/trailer-parts/155-r13-c-8-ply-4-on-5-5-pcd-wheel-assembly?gclid=CjwKCAjw46CVBhB1EiwAgy6M4p9ercGxIqbALR175vmPyQ7yHGoBoB2ZgauOx49sCyIsUpJrZqriMBoCYFcQAvD_BwE

Would love to hear any opinions from others who may have travelled this path, before I splurge more scarce funds! Thanks 

My local Tyre Fitter told me the same, when I ordered four for the Herald - that size is usually only ordered these days for small trailers. I ended up with five Firestone 155/80 R13s, on 4.5J rims.

[AlanT]

Thanks Everyone. 
Will either go 4.5s and 155s or take the plunge buy the 5s to fit the 175/70s, sell the mags.

[Pete Lewis]

there is the old addage that unless you change the pressures or load the footprint stays the same so going wide doesnt always give you anything but more drag

so the thinner will feel more spritely 

Pete 

 

 

[AlanT]

More about making the most of the investment already made @Pete Lewis I’ve got new tyres so, if I get 5J I can use these up whilst having the flexibility to go 155 in the future (should I wish).

165 would probably work on the Mags but it’s another risky investment vs going standard.