Tyre Help Required - Conflicting Info

goldcol

New Member
I have a Dawes Horizon whch has WTB Dual Duty XC 700c with cnc sidewall and Schwalbe Marathon, Kevlar guard 700x32. I am wanting to replace these prior to LEJOG with Durano's or Conti Grand Prix in 25s or 28's instead of 32's.

When I contacted Dawes they said not 25's but 28's will be fine, i contacted WTB who said 28's will fit but it is on the edge and that i should use 32's. A little confused to say the least, talk about conflicting info

Have any of you guys been in a similar position or used 28's, is this safe to do or to risk for the LEJOG.

Thanks
 

GrasB

Veteran
Location
Nr Cambridge
Measure the distance between the inside edge of the sidewalls. If it's 19mm or less then 28c tyres are fine, with it 22mm or more you'll have problems & if it's in between it's marginal. With the outer width at 24mm my guess it'll be somewhere around 19-20mm & as such marginal.
More info found here: http://sheldonbrown.com/tire-sizing.html
 
OP
G

goldcol

New Member
Thanks for the info. I will check tonight. If it is marginal what are the risks associated with riding that type of tyre when it is marginal. Have you run slightly smaller widths than advised.
 
OP
G

goldcol

New Member
Even more confused, WTB have confirmed inner rim is 19mm, so why did they say i cant run 28's when the chart from the website you found clearly does
 
OP
G

goldcol

New Member
Yes they sent the following email.

""Yes, you're right, it is possible to use this rim's width with 28's BUT if you have a look at the ETRTO (European Tyre and Rim Organization) chart attached you can see it is the MINIMUM dimension recommended. That is why WTB recommend a wider tyre for this type of rim. We have described the risks in our previous e-mail. It's for your own safety.""

which is still confusing as the ETRTO is saying you can as a minumum but it is within the guidelines, yet WTB are saying to use 32's for safety. It feels to me they are sitting on the fence and covering their ass.

 

GrasB

Veteran
Location
Nr Cambridge
I'm running 700x28c on 19.8-20.1mm rims (depending which vernier reading I believe, digital or visual) & have yet to have any problems. 700x23c tyres however can be pushed away from the rim under 80psi of pressure, also because the tyre is stretched there isn't much tread separating the rim from the road. These 2 in combination could be disastrous. What I did was ask my LBS if they had a 700x28c tyre they were going to throw out & they gave me a totally shot tyre but it let me see that a 700x28c was safe on the rims.
 
Top Bottom