Modern Tyres for an old bike

[splasher]

Hi,

I have a 1984 XR250 that hopefully will run nicely after an engine rebuild. Looking ahead I want to get it a daylight MOT so I can ride it to and from the local green-lanes. Tyres are proving thetrickiest as it has a 17" rear wheel and most modern tyres seem to be for an 18" rear.

I like the look of Pirelli MT21 Rallycross tyres and they are available in 17". The bike is currently fitted with 21x3.00 and 17x4.60. It's a stupid question I know but would modern 21F80/90 and 17R120/90 tyres go on the rims?

Thanks for any advice.

[Lutin]

Well now tyre sizes.

Front rim is 21" x 3", which in French Inches is 76.2 mm wide, so your proposed 21-80/90 tyre will fit the rim. The 80 is tyre width in millimetres and the 90 refers to the tyre height being 90% of it's width.

Rear rim is 17" x 4.6", which is 116.8 mm wide, again your proposed 17-120/90 tyre will fit the rim. So, the tyre is 120 millimetres wide and 90% of that high.

You may have to check that you have enough clearance though.

You might want to talk to these guys Trelleborg, as they may well be able to confirm the tyre sizes, or suggest others, for you.

Hope that is of some help.

[AIRWOLF]

90/90x21 front lots of choices.

mitas C02 130/80x17 is a good allround tyre and lasts well, i used them on my early xr250.

ps
Lutin,
where did you get the rim sizes from ????
front will be 21"x1.60", rear 17"x 2.10" or 2.50"

[Lutin]

ps
Lutin,
where did you get the rim sizes from ????
front will be 21"x1.60", rear 17"x 2.10" or 2.50"

Silly me, I was taking the tyre sizes as the rim sizes. Oops!

[splasher]

Thanks for the help guys. I wasn't struggling with the mm to inch conversion, I just wanted to make sure that the rim clincher profile hadn't changed or any other nasty surprises that would prevent new tyres going on old rims.

As an aside, I do find it strange that they quote the width of the tyre in mm these days but still use inches for the rim diameter!

[416cc]

I found that Pirelli MT21s were really good after there effort with MT17s. The 21s are good enough for longevity on the road & are reasonable on the muddy stuff unless it gets really soggy. I have raced in the trail bike class at an enduro using 21s, but when I moved up to the sport bike class I started to use MT83 Enduro spec Pirellis.

Watlings Welcome To Watling Tyres do a good deal mail order for bike tyres & they advertise in TBM.