CA – What wheels , what tyres ?

[JimPotts]

Has anyone got any ideas on what wheels and tyre options will fit a CA .Is there any tyre options for standard 13″ wheels ?
Thanks Jim

[TTotal]

Hi Jim,

I have 14 inch rims on mine, they use 185 by 14 and you can get great deals, I got Event Tyres (yes from China but for the mileage and speed we do good enough!) at £30 + vat each.

After paying £198 each for my TT rubber that’s CHEAP 😆

Cheers

John 🙂

[JimPotts]

Hi John
thanks for the reply , what rims are you using , are thet CF ?

[Phil Perfect]

The instruction books say :

10-12 cwt model 6.00-16, 4 or 6 ply tubed or tubeless (52-57)
10-12 cwt model 5.90-15, 6 ply tubeless (58-60)
10-12 cwt model 6.40-13, 6 ply tubeless (60 onwards)
15-17 cwt model 5.90-15, 6 ply tubeless (58-60)
15-17 cwt model 6.70-13, 6 ply tubeless (60 onwards)

Hope this help

[TTotal]

Ahhh…that accounts for the fact that my speedo is overreading – says 70 at 58 !

(Just knew Billy was lying when he told me he was going that fast ! 🙄 )

John 🙂

[trish1400]

Sorry to drag up an old post but I’ve been looking at replacing my tyres and just wanted to check I’ve the right size on currently. After reading this thread I’m beginning to think I don’t, as my speedometer is also over-clocking by about 10mph (not that I’ve ever got to 58mph – real or imaginary).

Right so:

• I currently have on 165 / 80 R13
• Mine is a 1967 long wheelbase model so according to Phil “15-17 cwt model 6.70-13, 6 ply tubeless (60 onwards)” Right?
• 6.70-13 = 175/80-13 according to this chart http://www.turbinecar.com/tires.htm

Therefore my tyres are too small….? and that’s why my speedo is out….?

Sorry – I’m so confused about what all the numbers mean. Any help appreciated!

Thanks,
Trish

[Gaz]

Hi Trish, I’ve read your post, but cannot give you an answer tonight, as my van is kept 4 miles away in my sisters garage. I know their 13″ but that’s it. I can check over the weekend if you wish. My speedo is fine.

[trish1400]

Hi Gaz,

Would be great if you could let me know. No rush though, I won’t be getting the tyres replaced for a couple of weeks yet (she’s currently not charging so I’ve got to get that sorted first).

Thanks,
Trish

[Colin]

My 1966 CA Workobus is fitted with Maxmiler tyres on the original rims (which I have had shot blasted and powder coated, and new chrome hubcabs all round). They seem to be excellent tyres and I use them on my trailer too.

The nice thing about them is that although they are radials, they have a nice crossply lookalike appearance which suits the CA much better than round-shouldered radials, which tend to look a bit sissy.

Take a look at my previous post on this topic:

https://www.dormobile.org.uk/phpbb/viewtopic.php?f=17&t=736

[trish1400]

A bit sissy? Haha – that must be a new adjective when applied to tyres.

Thanks for the reply – sorry I should have mentioned I saw your other post but you don’t mention the “other” number (I think it’s the aspect ratio – seems to be usually between 60 and 100) – to be honest I’m not really sure how that matters.

If yours are 175/80 looks like I’m on the right track – I take it your speedometer is ok?

Trish

[Colin]

Sorry, the full spec of the tyres is:

175 R13C 97/95 R LT. Hope this helps.

As far as the speedo goes, that’s pretty academic in a CA, so I haven’t given it much thought (Top speed of mine is 50 mph downhill, with a following wind and in neutral)

[ant]

Hi Trish
Be careful – the tyre Colin is talking about is 175×13 ie the aspect ratio is 100 (meaning the sidewall height is the same as the original crossply) In the example 175/80×13 the sidewall height is only 80% of the original, so the circumference is much less. Using 80 series tyres you’d have to go to 195/80×13 to get anywhere near the original rolling radius. As the aspect ratio reduces, you have to increase the tread width to regain the same circumference, and of course this means the tyres become too wide for the wheels.
Colin’s tyre seems a good choice to keep the original size and appearance, and they are also reinforced (8ply) as required by law on a CA.
Also keeping the original rolling radius means the speedo will read correctly.
Hope this helps,
Tony

[daveglanfield]

hi tony
i have got 6.70/13 cross ply tyres on my 1963 Bedford ca i have been thinking of changing to radial tyres what size sued i be looking for
dave glanfield

[ant]

Hi Dave

I was presuming Colin’s tyres were the correct size, but if Trish’s tyre chart is correct, 6.70×13 corresponds to 175/80×13 which means Colin’s tyres are too big,
and when his speedo reads 50 he’s probably doing about 70! 😀

After further research, it seems the exact equivalent of 6.70×13 is 170(/100)x13. See here :

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

Thus 175×13 is slightly bigger and 175/80×13 slightly smaller – take your pick!

[trish1400]

hmm 😯 😕 😯 Ok – I think I’ve got it now.

Thanks Ant – I’d seen that page but I couldn’t work out what use it was converting it to an 100 aspect ratio as kwitfit (or the like) don’t go up to 100. The chart that goes with that calculator is http://www.carbibles.com/vintagetyresizes.html but as it rather unhelpfully misses out 6.70/13 I’d ignored it. Looking at it again I realise that’s because you can’t get 180/80 tyres! So I guess if I went for an 80 aspect ratio I could get 175 / 80 or 185 /80.

I wonder if Colin’s aspect radio is slightly less than 100 anyway (is that what the 97/95 numbers in his last post relate to?), meaning his tyres are the perfect size.

So….. my tyres are definitely too small! Which is (one reason at least) why the speedo is out!

I’m really not bothered about they tyres looking ‘sissy’ and I’m definitely not going for an original look with my van (I’d love to but…). Right, so I’m off to investigate what modern tyres I can get for her which are 8 ply (arrgh, more things think about)!

Thanks everyone!
Trish

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