GT Grade / Stans Grail Spoke Problem

[bruce1530]

I’ve got the 105 version of the GT Grade, with Alex ATD470 rims. Have broken several spokes on the rear wheel over a year. Google suggests that I’m not the only one with this problem. Spoke to the supplying LBS, who confirmed that they had seen other bikes with the same problem, and rebuilt the wheel under warranty.

 

[I like Skol]

It is a bit odd to say the least! I bought my GT hybrid in 2010 and suffered a wheel quality fiasco before building my own which are now halfway through my predicted decade minimum lifespan.
My GT road bike bought in 2011 has been brilliant on the wheel front. I did rebuild the front to fit a group set matching front hub instead of the budget generic item but that wasn't really necessary.
The Grade 105 carbon wheels were shoddy.
Bought 2 x GT Avalanche MTBs in 2015. Wife's bike hasn't really done enough to say but son's bike has been suitably abused and comes out smiling.

Why can't GT consistently provide decent wheels?

 

[fossyant]

Manufacturers build to a budget, and wheels are usually the first bit not to match up to the rest. A set of basic Mavic Aksiums would be better than most factory wheels. They all do it.

 

[fossyant]

PS handbuilt are the best. Like Skolly, I've also rebuilt my wheels a few times.

 

[Roger]

I had the same problem with my Grade Alloy and Wiggle replaced the wheels with a set of Pro Lite same as @Ilikeskol. Wiggle told me GT and wheel manufacturer accepted it was an issue and would use double butted spokes on all new builds. I kept wheels and had them re-built to use with gravel tyres. I would push Wiggle for exchange, I mentioned the 'safety' word and them quickly agreed replacements.

 

[Heisenberg71]

Given the fact the bike is now about 20 months old Wiggle say it's out of warranty, which it is. However they said that if it was "the known spoke issue it would have shown itself before now". However they have agreed to refund me the cost of the rebuild to upgraded spokes and nipples onto my Grail rims and DT Swiss 240s hubs. Seems fair given age. I think I am also going to buy an upgraded set of wheels for the road, maybe even carbon. I can then keep the Grails for trails and gravel, which I would like to try more of.

It doesn't seem like a bad outcome really given age of bike.
Thoughts?

 

[Tenacious Sloth]

Given the fact the bike is now about 20 months old Wiggle say it's out of warranty, which it is. However they said that if it was "the known spoke issue it would have shown itself before now". However they have agreed to refund me the cost of the rebuild to upgraded spokes and nipples onto my Grail rims and DT Swiss 240s hubs. Seems fair given age. I think I am also going to buy an upgraded set of wheels for the road, maybe even carbon. I can then keep the Grails for trails and gravel, which I would like to try more of.

It doesn't seem like a bad outcome really given age of bike.
Thoughts?

I think that is fairly generous of Wiggle considering the age of the bike. Good customer support for a company of that size.

Graham

 

[Heisenberg71]

Refund received from Wiggle, fantastic customer service.

The DT Swiss spokes and DT Swiss brass nipples have made all the difference. Wheels are a LOT stiffer and no signs of spokes coming loose or snapping. LBS fitted some dodgy and very stiff /sharp adhesive backed rim tape that when it became creased caused a frustrating run of subsequent punctures until I figured it out. However now remedied and we're back on the road.

Thanks for advice everyone, awesome as always.

 

[Yellow Saddle]

. May have been the quite potholy road surface proceeding it.

Potholes have absolutely nothing to do with broken spokes or nipples. Much has been written here about it before. I recently explained why. A search should reveal the post.

.

However the following day suddenly another one goes in the rear, then one in the front, both again at the nipple. I have never had any spoke snap on any bike, but three spokes in two days in two separate wheels? Crazy and surely indicates a fault or metal fatigue potentially? Finished the ride one spoke down in each wheel praying it would survive, which it did. Wheels slightly out of true but not drastic.

That's the standard mode for fatigue breaks. Spokes all fatigue at the same rate, so if you experience one fatigue break, it is an indication that the others will go soon as well. A good mechanic can distinguish between a fatigue break and a "Snapped" spoke. The latter is caused only by an object such as a stick, thrown into the spokes. There's a big difference and the course of remedial action differs.

I have contacted Stans to see what they think, as well as Wiggle who sold the bike originally just over a year ago. Not holding out much hope and thinking it may need to be fixed not replaced. Stans Grail Rims and DT Swiss hubs are awesome so I am assuming I could get them re-laced or even do it myself potentially.

Stans makes excellent rims but have no clue whatesoever on wheelbuilding. I've participated on the Stan's forum for years and have never had any confidence in the mechanical engineering talent at that company. The company's online record of advice reads like a fairy-tale.

Your thoughts on cause of three snaps in two days?

Recommendation on heavier duty spokes?

If DIY how do I correctly measure / specify the right spokes?

The spokes broke for two reasons:

1) They are the notoriously rubbish DT supercomp spokes which have a 1.8mm thread, 1.7mm shaft and 2.0mm elbow. This configuration is make by idiots for idiot builders. DT-Swill post-rationalises the bizarre butting by using words like "lightweight" or something to that effect. The real reason for a 1.8mm thread rather than a 2.0mm thread is that a 1.7mm spoke (1.7mm in the shaft that is) is reasonably difficult to build with because the slender shaft easily twists and machines can't cope with that, only skilled humans. To reduce the friction that causes the twist, the spokes have 1.8mm thread which produces MUCH less friction than a 2.0mm thread. Therefore the spokes will twist less. However, a 1.7mm spoke resists torque quite poorly because the resistance to windup reduces by the fourth power of diameter. A small, 0.1mm difference in shaft difference has a large effect on resistance to torque.

The spokes broke because the thread's roots are deeper than the outer diameter of the spoke, making the roots about 0.1mm thinner than the spoke itself. This causes a highly stressed weakness at the first thread just inside the nipple that propagates fatigue cracks. This problem doesn't exist with 2.0mm threads because the thread roots will be thicker than the 1.8mm dia of a standard double butted spoke and much thicker than the 1.5mm dia of a Revolution spoke.

In summary, the spoke broke because of the stupidity of DT Swiss and the gullibility of the marketing-oriented pseudo-engineers at Stans.

You had three spoke brakes (not snaps) because fatigue sets in equally on all spokes. Wheels are round, after all and all spokes get equal load cycles.

You don't need heavier duty spokes but proper spokes. Standard double-butted is the best solution.

Given the fact the bike is now about 20 months old Wiggle say it's out of warranty, which it is. However they said that if it was "the known spoke issue it would have shown itself before now". However they have agreed to refund me the cost of the rebuild to upgraded spokes and nipples onto my Grail rims and DT Swiss 240s hubs. Seems fair given age. I think I am also going to buy an upgraded set of wheels for the road, maybe even carbon. I can then keep the Grails for trails and gravel, which I would like to try more of.

It doesn't seem like a bad outcome really given age of bike.
Thoughts?

Wiggle is just avoiding the real issue because they themselves don't understand the problem. Of course that issue has shown up before but no-one is putting 2 and 2 together. Their service is good though. You had a good outcome.

BTW: 1) the bike mechanic that said those spokes were straight-gauge doesn't know what he's talking about.
2) There is no such thing as stainless steel nipples, just brass or aluminium. Aluminium is rubbish.
3) Forget about carbon rims. They have other problems you don't want.

 

[Heisenberg71]

Very thorough and informative response, thank you.

 

[Qisope]

I wanted to add my piece as I got the same issue with the GT Grade Carbon 105 and notubes grail wheels.
2 spokes broken on tarmac with no apparent reason.

The bike has been bought from Wiggle a little over a year ago (August 2016).
I have been denied access to warranty with the advice to reach a local supplier for repair.

I think I'll just buy a new set of wheel somewhere else and avoid GT and Wiggle for a while.

 

[Mr potts]

bought a gt grade full carbon ultegra from Hargreaves of Dewsbury in 2016, had the same issue with spokes breaking, after a couple of visits to LBS i took the wheels back and they respoked them with something a lot stronger and " touch wood" never had an issue since with the spokes, but like Heisenberg71 then suffered with pinch flats, turns out the tape was crap, even had a tyre explode in the club house after a ride resulting in nearly giving all the old boys a heart attack!!
Was thinking of upgrading to something lighter and faster, any ideas?