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Change from 700x35c to 700x40c knobbies
#1
I have two trek bikes, a road bike and a trek 7300 hybrid with 700X35c tires. I often take my dog with me using a walky dog (a mechanism to attach a dog leash to the bike) bolted onto the seat tube of the hybrid. We often go off street. Nothing like single track but sometimes grassy fields, dirt paths, gravel roads and the like. I'm thinking of a 700x40 tire with a more aggressive tread. I'm not concerned with speed, that's what my road bike is for. The 40 should fit my wheel but I'm not sure if it will fit my frame.

Dan...
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#2
Very cute dog and glad there is yet another fellow cyclist that takes the dog along. I am thinking that the 40c step up should fit ok. Just make sure your wheels are in true so you don't get rubs. There is someone here who went with snow tires (Joe_W?) and they were slightly bigger I believe. Wait to see if one of the other members can verify this.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#3
Hard to tell (crystal ball off for polishing ...) from here. I went up from 700-23c to 700-35c in the front (Schwalbe Marathon Winter) and 700-30c in the rear (Schwalbe CX Pro) on my Peugeot road bike. Since it is a road bike, tyre clearance was a problem (otherwise I'd also run 35mm in the rear). In summer it's CX Pro front and rear. Your bike looks as if it can handle much more. Take a look at the following spots to guesstimate whether you can run one size bigger:
- fork crown
- rear break bridge
- seat tube (I cannot install the wider tyre, I cannot get the axles in the dropouts since the tyre cushions against the seat tube)
- fenders?

5mm wider tyres are 2.5 mm "higher" which is not that much.
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#4
I just replaced the standard Continental 700x35c with Kenda Kourier K-Shield 700x40c tires on my Novara Forza. After quite a lengthy ride over mountain pot-hole, rock strewn roads and off-road dirt paths, the replacement seems to have been worth the effort and quite compatible with no adjustments necessary. I ride primarily in the mountains and along unpaved coastal paths and needed a more rugged all-weather tire.
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#5
Cool! nice pic
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#6
(03-26-2010, 11:15 PM)danr2013 Wrote:  I have two trek bikes, a road bike and a trek 7300 hybrid with 700X35c tires. I often take my dog with me using a walky dog (a mechanism to attach a dog leash to the bike) bolted onto the seat tube of the hybrid. We often go off street. Nothing like single track but sometimes grassy fields, dirt paths, gravel roads and the like. I'm thinking of a 700x40 tire with a more aggressive tread. I'm not concerned with speed, that's what my road bike is for. The 40 should fit my wheel but I'm not sure if it will fit my frame.

Dan...

Dan;

Time to get out your ruler. Measure the clearance side to side and up to down on things that come close the tires. A 40x622 is 5mm wider and 5mm taller than a 35x622. Thus you need about 10mm clearance radially (up-down) and 5mm laterally (side to side). You only half as much laterally because half of the additional width goes to each side.

Most bicycle tires are have 100% aspect ratios, meaning that their width and height (from the ERD) are the same.
Nigel
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