Crest Mk3 Rim Cracks... and now my Flow Mk3

[RobertWhitehead]

According to the LBS they've been having issues with the cracking of the rims for the past 5 years. Apparently they are getting fed up having to rebuild the wheels for free, and this is just one shop. I am not a big fan of Stans. Everyone I know whom had a set had issues. And yes there will be folks who have never had any problems with them. Luck of the draw I suppose

[MudLark]

According to the LBS they've been having issues with the cracking of the rims for the past 5 years. Apparently they are getting fed up having to rebuild the wheels for free, and this is just one shop. I am not a big fan of Stans. Everyone I know whom had a set had issues. And yes there will be folks who have never had any problems with them. Luck of the draw I suppose

I suspect that part of the problem is that very few bike shops actually use spoke tension meters when building wheels. I've yet to see a techie using one in my lbs - which is a very busy and reputable shop. These rims are clearly on the engineering margin and while they might crack anyway, not building the wheel absolutely correctly and within spec probably doesn't help either. Whatever the case though, wheel failures can sometimes mean a very long walk home or sometimes a bad crash.

 

Reason I'm asking is I've just stuffed a pair of Bontrager carbon rims (Kovee 23s) and I'm wondering about just fitting aluminium instead. The old debate.

[Quagga]

Sooo... no more posts in the last 2+ years about these rims cracking. Have Stans solved the problem with their changed heat treatment?

Not sorted. I chucked my 3rd replacement rim when Droo opened after lockdown last year for a WTB

[MudLark]

Not sorted. I chucked my 3rd replacement rim when Droo opened after lockdown last year for a WTB

 

How much do you weigh and had they been properly set up with spoke tension measured etc?

[Quagga]

How much do you weigh and had they been properly set up with spoke tension measured etc?

All 3 rims were built by 3 different well knows wheel builders. Spoke tension meter was at least twice.

 

I am 90kg and this was on my hard tail Niner that was used for my 14km each way tar commute.

 

The last rim saw 15km of gravel road in a year according to Strava.

 

These rims all crack every 2nd spoke, drive side rear.

 

Myself and two other friends had the same thing. Rear wheel drive side cracks. The weigh 80kg and 78.

[Skoffel]

Also had it on my previous bike and had to replace my back rim every 18 months due to cracks

[RiverInTheRoad]

My Flow is also cracked. I plan to ride it till failure. DT Swiss here I come

[Rust Never Sleeps]

Had same issues with Stans Arch.Several times.Eventually I got fed up and bought DT Swiss.2 years of riding,absolutely perfect

[MudLark]

Thanks guys. Interesting. Seems that they crack on the back wheel then. Maybe okay for the front.

 

Rust, which DT Swiss rims are you using? On another thread some folk were complaining about them too. Something about made of cheese....

[Quagga]

Thanks guys. Interesting. Seems that they crack on the back wheel then. Maybe okay for the front.

 

Rust, which DT Swiss rims are you using? On another thread some folk were complaining about them too. Something about made of cheese....

Correct.

 

I still have the very first one on the front when I bought the set. 

 

So Front is fine, but as a rear wheel it is not

[M L]

After washing my singlespeed last night and inspecting my rear Flow rim....

Guess whats starting.

 

The bike in question...

SeanSIR9.jpeg

 

2 of the cracks... there are 4

CrackFlow1.jpeg

CrackFlow2.jpeg

 

 

2600km done on them, bought in March 2017

Very very nice Sir.

[MudLark]

Correct.

 

I still have the very first one on the front when I bought the set. 

 

So Front is fine, but as a rear wheel it is not

 

Thanks Quagga. I think I am maybe just going to get another set of carbon rims then. Probably buy a good second hand set. There's no point in messing around with something which is going to give trouble – or may give trouble. I ride solo most of the time and sometimes on quite remote roads; the last thing I need is a wheel failure when I'm in gramadoela country. 

[MarcHD]

Thanks guys. Interesting. Seems that they crack on the back wheel then. Maybe okay for the front.

 

Rust, which DT Swiss rims are you using? On another thread some folk were complaining about them too. Something about made of cheese....

 

You don't perhaps know what thread this is as we (DT Swiss SA) would like to assist where possible...

 

There are a number of causes for rims failing prematurely, many of which are intermarried. Hopefully we can shed some light on this below...

 

1. Spoke tension.

Even the strongest rims in the world will eventually crack at the spoke/nipple holes if the spoke tension is not optimal.

This is due to the amount of flex spokes undergo in a typical ride as the loads change on the wheel. As an example: when cornering the spokes on the lower half of the wheel will have a reduced load, causing them to slacken a bit, while the opposite is true of spokes at the top half of the wheel. If the tensions are below optimal this slackening with load changes will be increased of course, and over time this constant tugging on the nipple will pull it through the rim. The lower the tension, the harder the tugging. 

 

2. Intended use and Weight limit (ASTM classifications)

This part is often overlooked, but it incredibly important. All manufacturers have a very specific target market for which they intend a specific rim (or any product) to be used for. If, for example, you are using a product outside of this intended use and/or weight limit, a brand is well within their rights to deny any warranty for premature wear or breakages. 

 

3. Correct tools and best practices. 

This ties in somewhat with point 1. but it should stand to reason that a self proclaimed wheel builder should use certain techniques and tools as a MINIMUM requirement. 

This includes things like a spoke tension meter, spoke prep/nipple thread lock, destressing the wheel during builds, correct lacing methods (yes there is a correct way and wrong way) and any parts specifically required by the manufacturer. For example: DT Swiss rims using thin wall technology require the use of PHR washers and matching nipples as the rims have been carefully engineered to pair with these specific nipples.

 

4. Fair use/abusing products.

Again, this ties in a lot with point 2 and shouldn't need to be touched on really, but if you are using an XC rim to huck road gaps.... do not expect them to last! 

 

5. Spoke choice. 

Also largely overlooked. "A spoke is a spoke" Is not something you ideally want to hear from your wheelbuilder. Spokes vary hugely in their quality and their intended use! 

A thin spoke might save you some grams, but it will not be able to be tensioned to the same loads as a thicker spoke and as we mentioned above, this lower tension will cause more flex in the spoke and possibly expedite the premature breakage of rim/spoke/nipple. 

Further to this, not all spoke are created equal, and while most of the time you will probably not notice (or care) about the difference in spokes, the reality is the quality control and manufacturing techniques vary greatly from brands and a premium spoke will certainly outlast an inferior one

 

6. Spoke lengths 

Again, sometimes overlooked. Although thankfully most wheelbuilders understand this concept very well. The length of the spokes need to be as close to perfect as possible. It's a widely accepted practice for dealers and distributors to only carry even length spokes (carrying the odd ones as well would cost a fortune) and there is nothing wrong with this as long as the spokes are within an accepted tolerance for the given nipple choice. Example: if a spoke calculator indicates an exact spoke length being 295.5mm it is perfectly acceptable to upsize the spoke to 296mm ONLY if a rear drive nipple is being used. Alternatively if a standard nipple is being used a downsizing may be required. However as is the case in this specific example, it's not likely a store will carry a 295mm spoke. It is not best practice to downsize to 294 as this is a difference of 1.5mm and may cause the nipple to be compromised in strength as the spoke thread is not perfectly mated with the nipple thread. In this case opting for rear drive nipples, even at the greater initial (and unexpected) cost as it will very likely save you lots more money in the long run! 

 

 

 

Hope this helps clarify things - let me know if I left anything obvious out!

[Alouette3]

My rear DT rim is splitting at the rim joint at the bead and leaks sealant, so have had to seal it up. Though to be honest, probably find this could be due to an unlucky placed rock strike on the trail . Also the cheaper M1900 rims and at only 22.5mm ID, will like take the opportunity to fit wider rims when the kitty is built up again.

[MarcHD]

My rear DT rim is splitting at the rim joint at the bead and leaks sealant, so have had to seal it up. Though to be honest, probably find this could be due to an unlucky placed rock strike on the trail . Also the cheaper M1900 rims and at only 22.5mm ID, will like take the opportunity to fit wider rims when the kitty is built up again.

 

Bummer! Sounds like you should be upgrading to the E (for enduro) family of rims. Unless it is as you said - an unlucky placing of a rock strike precisely at the join. 

 

Give us a shout when you are ready and we will do our best to assist in replacing for you. 

 

Regards, 

[Headshot]

It would be lovely if all rims were simply made strong enough to withstand the rigors of MTB.... There are so many bikes that come out with the bare minimum in wheel strength and rubbish hubs to match. By all means make them heavier and stronger, but not heavy and weak. 

 

Some of the issues with modern wider rims is that manufacturers have attempted to make rims that weigh the same as much narrower, smaller, rims. The net result is a weak and failure prone rim like the Flow mk3's. 

 

Rear rims take a beating and will always crack eventually. The question is what is an acceptable life span? There are so many variables perhaps its best to simply buy cheap rims and bank on replacing the rear one once a year? A DT costs what, R2400 or more a pop. That's 2 or 3 cheaper rims and you're spreading the expense.