Tyre Sizing

[kevberlin]

My Cb250rs requires a new rear tyre. The owners manual gives the tyre size as 400s 18 4PR. My current tyre shows itself to be 110/90/18.
I understand the 110/90/18 description, but haven’t a clue regarding the 400s 18 4PR.
Can anyone enlighten me please so I can be assured when I purchase the tyre.
Thanks a lot.
Kev

[xbally]

Sorry Kev I have no idea but when I get some time I intend to look into this as the tyres on my RS250 will need replacing soon too.

[xbally]

My Haynes says 4.10 S18-4PR for the rear. Mr. Honda's owners' manual also says the same.

[Ian]

I'm no expert on tyre information but I believe the 4PR is 4 ply rating. This is an index that measures the tyre's capacity to withstand the load at a given pressure.

[kevberlin]

It seems the 400 sizing shown in the manual is the imperial measurement.
In the case of the cb250rs 110/90/18 is appropriate.
Kev

[Itsme]

Being pre-metric I was always used to buying tyres in sizes like 3.25, 3.50 and 4.00 x 18 or 19. The 4.00 refers to the width of the tyre in inches (remember them?) and confusingly the .25, .50 etc was a fraction of an inch in metric! or at least that's what I always was told and if you measure the width of old tyres it seems to be right. In those days we didn't care about aspect ratios, the middle number of a modern tyre size, we just bought the right rim size and a suitable width for the bike and how we were going to use it. So on a 250 a 4.00x18 sounds about right and I would have expected the front tyre to be a 3.25 or 3.50.

Ian

[iansoady]

I prettty much agree Ian, although I would use a size lower - 3.50 for the back and 3.25 for the front. I need a back tyre for the dreaded Yam and intend to fit a 3.50x19 Mitas H01 which I've had success with in the past.

[Itsme]

Hi Ian

To be fair on reflection I agree with your choice of tyre sizes. I remember my 350 JAWA using a 3.50 x 18 rear and a 3.25 x 18 front. I think looking back the only time I used a 4.00 x 18 on any of my CZ/JAWA machines was when using them with trials tyres and then I used a 21" front wheel with the 18" rear.

Ian

[xbally]

Kev - did you get your tyres sorted as I'm thinking of replacing mine over this coming winter and wondered how you got on?

[kevberlin]

Hi Martin. It was all simple in the end as I had the same size rear tyre fitted as was removed. Namely,  110/90/18.
If you wish me to check what my front is size wise, I will have a look tomorrow and report back.
Phil Saunders at Ludlow fitted the tyre for me. He’s a top bloke, old school and trustworthy.
All the best,
Kev

[xbally]

Thanks Kev.

What make did you go for? Everything I've seen is coming up rather expensive when you think of the relatively low loads this bike will place on its tyres.

Yes it would be a help to know the size of the front too.

I did look on the website of your local chap earlier today.

Cheers.

Martin

[iansoady]

I've had extreme difficulty findig a suitable tyre for the back of the little Yam and finally decided on this:

https://tyretectrading.co.uk/tyres/cst-c6017-motorcycle-tyres/

Cheap enough an given the use I'll put the bike to it will be OK. It's in my garage now waiting foir me to have the enthusiasm to fit it. It does seem very stiff....

It's 100/90x18 as I couldn't find a budget 110/90 profile tyre but is compatible with the 2.15 rim.

[xbally]

Thanks Ian. That's a really useful link. They seem to have a good range and I'm sure I could find something appropriate. Prices also  seem good.
My problem is it must be nearly 50 years since I last tried fitting a tyre myself and I recall the battle it was. Even in the late 70's there was  a local motor cycle tyre specialist who would do you a deal and fit them.
 The RS250 has DID alloy wheels with very soft rims.
I really need a local ish contact to fit them but if I buy online and not from a local source expect to be stung if not buying from them.
I looked at Wheel House Tyres (Birmingham area) but don't fancy the trip via Spagetti Junction nor could I readily find what I wanted at a reasonable price unlike in your link . I must be getting really old in my outlook!
I don't mind travelling a reasonable distance but the journey has to be pleasant - not stuck in traffic on the M5 / M6 / M42!

[kevberlin]

Martin,
The front tyre is a Continental shown as a Contigo.
Size is shown as 3.00 - 18 m/c 52P
As regards my rear tyre, upon checking it I noted it was 20yrs old and unsurprisingly the ride was harsh. I bought a new tyre. My viewpoint in choosing the new tyre was that the 250rs is a lightweight bike, I’m lightweight and the bike gets ridden only in the good weather in a way that respects its 40+ yr age. I bought a Kenda simply because it came up at sensible money. I didn’t see the point of going for a “performance tyre”.
The old tyre was a nightmare for my bike shop to remove due to its age and despite him having a pnuematic tyre machine.
Hope this helps with your decision making.
Clearly, others may see things differently.
Kev

[xbally]

Thanks Kev,

That's helpful.

My tyres were IIRC fitted to the bike not long after I acquired it.  I think it's got a Mitas or some such on the front and the equivalent of a TT 100 (Dunlop) on the back .I've owned this RS for about 10 years although I've owned others as well over the years.

By any reckoning therefore the tyres are like me and well past their sell by date although I can't detect any cracking and the treads are IMHO well up to the legal limit. The rear though has  always lost pressure when I remember to check it. I suspect and hope though that new rubber will hopefully make the ride less harsh, as along with the snatchy nature of the transmission (inherent in most singles  think) this is one of the minor irritations of the model. Oh talking of which mine has always had a small oil leak from the cam cover head area in a most unHonda manner which I've never been able to cure.

As I said in my reply to Ian I'm very wary of changing the tyres myself . I know of a couple of local workshops who will supply and fit new tyres but I don't think they will offer anything like the choice that Ian's link does. I think I may also need new tubes given the age / difficulty referred to above. 

Like you I only  ride in good (99% dry) weather and am no heavy weight nor do I ride the RS fast or get it cranked over very far these days. I therefore consider as you did that a "performance" tyre will be excessive.

The Kenda seems to fit the bill exactly in terms of price and performance although Ian's link also offer other good priced options.

I'm going to make further enquiries and shall report back when I can.

Thanks to all.