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My bicycle: GT Grade Alloy 105 year 2015

After ~2 years riding i've broken 4 spokes (1 broke, fixed, 1 broke, fixed, 1 broke, fix, and now broke again). At this point from what I understand I need a new wheel.

From what I remember I got all the default parts: http://www.gtbicycles.com/usa_en/2015/bikes/road/adventure/grade-alloy-105#bottom-products-area

I don't want to spend too much but I am also heavyset 250lbs (114 kilograms) and usually spend my time in the seat, there are parts where I go fast so the rear wheel will take some punishment.

I don't think I need to switch my front wheel yet unless it makes sense. How do I figure out what kind of wheel I can get where i wont have to change other expensive pieces of my bike? What are the parts that I need to look at?

  • I went from 32 to 36 spokes when I had the chance, and I'm ~100 kilos. The rear wheel is the least aero area on the bike, so higher spoke count doesn't matter as much. – Criggie Nov 18 '17 at 20:25
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Specific product recommendations are off-topic here but we can provide some guidance that will help you choose an appropriate wheel.

You can replace both front and rear wheels without having to replace any other components. For the rear you have to move the sprocket cassette to the new wheel. This requires a special tool but is straightforward. Disc rotors must to moved to both front and rear wheels of course, and front and rear calipers will also need re-aligning.

You have to know what the specifications are so you can select a compatible replacement wheel. The fixed things are:

  • Rim diameter - 700c / ISO 622
  • Hub width - 135mm rear, 100mm front in your case
  • Quick release or through-axle - quick release rear , 15mm through axle front in your case
  • Rotor attachment - 6 bolt.
  • Number of speeds - Some 11 speed systems require a slightly wider freewheel body, I'm not sure if Shimano road 11 speed does. Hopefully someone else can fill in this detail. In any case you want a hub compatible with Shimano 105 11 speed.

You get to chose the spoke count, rim width (to support the tire width you want to run), rim profile and tubed vs tubeless.

You should consider a higher spoke count with 3 cross build for higher strength than the original wheel. The GT page you referenced says the rear is 32 spoke. I'd say you want a minimum of 32, consider 36. When it comes time to replace the front I’d go for more spokes there too.

According to the GT page referenced the rim width is 22mm, good for 28mm and wider tires. If you are happy with the original 28mm tires or want slightly wider I’d stick with 22mm rims.

The big benefit of tubeless is the ability to run low pressure and not risk pinch-flats. You can look up pros and cons and see if you want to go that way.

Addressing buying options - if you don't know much about wheels don't buy individual parts and have wheels built. There is a bewildering array of rims hubs and spokes. You can either:

  1. Buy a pre-built wheel of a known quality brand such as Mavic or DT Swiss.
  2. Use an online custom wheel site such as wheelbuilder.com. Pick from one of their hub-rim-spokes options. You can contact them and see what they recommend.
  3. Work with your local bike shop, they will be able to recommend some specific options also.

If looking at pre-build brand wheel, look for 'gravel', cyclocross (CX) or perhaps 29" MTB wheels (29" is same as 700c) as these will be built for more strength (at the expense of weight).

Note that many wheels and hubs are now built for through-axles but come with quick release adapters.

  • Are you sure hub width is 130mm (instead of 135mm)? Not saying I know otherwise, but that would be very surprising for such a recent bike to use a very rare/deprecated disc-brake hub width. – Hans L Nov 18 '17 at 3:08
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    @Hans L I have a carbon SRAM Force GT Grade. I thought I measured the rear dropouts at 130mm, but I just checked and it is in fact 135. Thanks for the catch! Answer updated accordingly. – Argenti Apparatus Nov 18 '17 at 3:50
  • @ArgentiApparatus if I have 32 spokes - should I go for 36? – StanM Nov 21 '17 at 16:53
  • also what does 'Formula Ultra light 6 bolt disc sealed casette, 32h' mean? what's 32h - is this the number of spokes? - if a buy a whole new wheel, the hub comes with it I just realized... would it be cheaper to get the new rim+spokes? or i should change the hub as well? (sorry I don't know anything about wheels) – StanM Nov 21 '17 at 16:57
  • If you need a stronger wheel, more spokes is a way to do that. The other is a better quality wheel with stronger components and higher build quality (higher, more even spoke tension). 'Formula Ultra Light' is just what GT calls their non-name brand hubs. '32h' does in fact refer to the number of holes for the spokes. Personally I would get a replacement wheel (or wheel set) not rim and spokes as you will then have to have the wheel built and you'll have a lower quality hub than the rest of the wheel. – Argenti Apparatus Nov 21 '17 at 17:14
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I would first say that the reason the spokes are breaking is a problem with the wheel. The breaking spokes were most likely a symptom of a poorly built wheel and not necessarily an under-built wheel. Spokes break when they go slack (and then are put back under tension); it is likely that the wheel was under-tensioned or unevenly tensioned, which is also why the spokes kept breaking.

That said, I'd agree with Argenti. A 32h wheel is going to last longer than a 28h wheel and would definitely be my recommendation for someone over 200lbs.

If you can, though, I strongly encourage you to get a hand-built wheel. It will cost you more, but it will last many times as long as a factory built wheel. Alternatively, you could buy a factory wheel but then bring it to a wheel builder to have it checked -- and likely rebuilt (detensioned & retensioned).

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