Tyre help please ...


All these threads about the fairy have finally got to me. On the way home tonight, about 7 miles into my 13 mile rural commute, rain coming down and dark, I started to feel a bumping sensation on the back wheel. I carried on home with strange handling at the back. Checking the tyre I found that it had a large hole, maybe 7 or 8mm diameter and the inner tube was pushing through creating a distorted bulge. Fortunately I had suffered from the fairy back in September and put some slime tape in the tyres, this had stopped the loss of air this time. Enough of the saga, now the question ...

The bike is a Giant Cypress and has 700Cx38 tyres, do I have to stick to this size (the 38 bit) or can I use narrower a narrower tyre?
That depends on your rims, check them out on the manufactures website for tyre sizing.


New Member
mickle said:
Measure the width of the rim, you can use any tyre which is the same width or wider. The upper size limit is determined by frame, brake or mudgourd clearances.
The inner width our outer width?


Senior Member
mickle said:
I'd have said outer width actually but am willing to be proved wrong.
The outer width obviously includes the width of the braking surfaces and structual aspects of the wheel. It would not affect the ability to hold the tyre surely as it sits on the inside?

For example, my clunking great mavic A719s are "ETRTO compatible size: 622 x 19c" They are 22.5 when measured externally with a caliper. http://www.mavic.com/road/products/A-719.324119.aspx#moreinfo


Thanks for the help. I have been to my LBS and purchased some 700x28 (downsized by 10mm!) Continental Contact tyres with their 1 year puncture guarantee. Trouble is I now have a cold and don't want to die on my commute! so haven't been able to try them out yet.

Elmer Fudd

Miserable Old Bar Steward
I always believed you should measure inside the inside of the rim, not between the beads, for this you need some engineering callipers or a vernier with some decent cutouts at the bottom of the legs so you can get inside the beads.
Of course, I may be talking total bollix (again !).


New Member
Hairy Jock said:
Well let us know how you get on with the 1 year p***ture guarantee, not heard of that one before.
Well I tried Conti Contact Sports last year because of the guarantee, but the tyres turned out to be made of cheese - punctured several times and wore down within a few months. I bought online so the guarantee meant sending back to the vendor - I didn't bother, and I didn't want another set anyway. I suspect the guarantee is a substitute for genuine, built in puncture protection. Generally I think the Conti's use too soft a rubber compound. Tyres like Schwalbe Marathons and Spesh All conditions pro (which I use) don't have such guarantees, but they don't puncture either in my experience.
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