Interview: Downhill Wheel Tech with DT Swiss

Next in our tech deep dive series is DT Swiss. The Swiss wheel manufacturer has been making wheels for 25 years, so they should know a thing or two about what makes a good downhill wheel. DT Swiss has notched up plenty of downhill World Cup wins, with their rims and wheels becoming a mainstay of downhill racing and a firm favourite among privateers. So much so that they have a service pit on hand at the World Cup to help riders with wheel builds and maintenance, ensuring the world's fastest riders keep rolling.

We spoke to DT Swiss's Chris Brattle and their wheel builder Swen Heil for their input on DH Wheels and some tips on tubeless setups. Then, Continental Nukeproof's Jack Chapman gives us a team mechanic's point of view, along with Ronan Dunne, to get the rider's view of DT Swiss Wheels.

DT Swiss: Chris Brattle and Swen Heil

Your new wheels the FR 1500, came out this year didn't they?

Yep, these were launched at the first round at Lenzerheide. So new wheels this year, the new FR 1500s. These are our new premium downhill race wheelset, although actually, they're significantly lighter than the previous version, the old FR 1950, which was a bombproof wheelset that was a bit chunky. The new FR 1500 is actually at the point where it's actually viable for sort of heavy-duty trail bikes and super-enduro and things like that. It's a bit more of a versatile wheelset. The big thing this has of course, is the new exp hubs, which are some of the lightest hubs on the circuit, still some of the most reliable, easiest to service etc. And, of course, the new FR 541 rim. Based on our multiple World Champs and World Cup winning EX 511, which you still see everywhere, it is very similar overall. The big difference it has over the EX 511 is the size of the bead, you've actually got a wider, blunter bead there, which makes it harder for it to cut into the tire. In lab tests, it takes about 70% more actual kinetic force to pinch a tire versus the EX 511 and that's what you're really gaining from that new design.

So you're just going to see much less kind of pinch flats on the side of the tire?

Pinch flats are 95% luck. Yeah, there are so many variables, for instance, one thing we're seeing a lot is different suspension setups can actually have a massive effect on how quickly you go through rims. So there are huge amounts of variables, but all of those things in isolation, you're looking at about 17% more force to pinch flat a tire. In reality, the riding styles will have more of an effect on it, but every little helps.

Are tire inserts a big thing that you factor in now? Is it a thought process?

In a way. A lot of people don't like the feel of tire inserts, quite a few of the World Cup teams aren't using them. It's an optional thing. Some riders really like to feel them or like to run particularly low pressures and the added support that the insert gives. Others really don't like that feel. So that's very much a suck it and see. Rider style, suspension design has a big effect on that. We're happy for our rims to be used with inserts. The only thing is, we are talking about foam inserts here. The only potential issue is the inflatable inserts. The thing with them is they put a lot of pressure on the inside of the rim and actually, it's the equivalent of running a very high or like a road tire kind of pressures in them and if you haven't slackened off the spoke tension and built the wheel for that pressure this can then lead to wheel issues down the line. If we're using one of those inflatable inserts that pressurise the rim you'll need to install it and then check your spoke tension to make sure that works.

What tips do you have for people setting up a wheel for tubeless?

Firstly, make sure you've got the rim properly clean, ideally use a good, strong degreaser on it to make sure you've got any sort of grease or gunk removed because it will improve the adhesion which means you get a nice flat finish and you're much less likely to get a sealing mount to work its way underneath.

Second thing, make sure you've got the right width tape for the rim. Most rims are measured between the internals of the bead hooks, so for instance this is a 30mm rim. Ideally, you want a rim tape that's going to cover all of the bed of the rim, to actually tuck under the bead hooks. So for this we're going to use a 32mm tape. In an perfect world you also want a rim tape that's ever so slightly wider than the rims internal width.


Always start at the spoke hole at the side of the valve hole, because you'll use that to anchor it at the end. One thing that can happen with a lot of tape, including ours, is if it's really, really cold the glue doesn't activate so, I mean, we've had Fort William World Cups where it's been really, really cold and there have been times where I've just stuck inside my jacket, under my armpit, to warm it up for 10 minutes, not possibly the most hygienic solution but it just means the glues a bit warmer, you can just leave the tape on the radiator or something if it's cold day. On a normal warm day or spring day it would be fine, but in the winter it's good to warm the tape up.

So start at the valve hole go a little bit past and get your thumb in there to get it nicely pressed down. The big trick with the tape is get a lot of tension on it, do nice big sections so you can line up easily, and you follow it with a thumb to make sure you get rid of any wrinkles. You can always pull it off again if it doesn't go quite right. Slow and steady wins today. Just lay on slowly and keep that tension on it, don't let it off because if you do, you'll get a wrinkle which will allow sealant to get around the edges and under it. You just overlap it by one or two spoke holes, it's not a precise science as long as you have a nice overlap. It also depends on how warm it is, if it's nice and warm, the glue works well and you need less overlap.

If you're worried about a bit of wrinkle it doesn't matter too much if it was a double-layer section but a single-layer section you want to make sure you haven't got any wrinkles. Just check it around to see - it should all look lovely, smooth and centred.

Next you need to put in the valve stem. There are several ways to do this, however we recommend firstly to make sure you got your tape overlapping past the valve hole, then feel with your fingers so you line up the valve stem with the hole and just push it through the tape with the valve closed. Make sure it's fully seated down. It does not need to be super tight, if you need to do it up with a set of pliers there's probably something else going on there and you can actually end up breaking the bond between the valve core and the rubber on the end of it and you end up having a valve failure down the line which is really tricky to fix. So just finger tight.

Is there anything that you do different wheel build-wise for the downhill riders that you would do for any other disciplines?

It's dependent on the track and the bike, specifically the fork. So we're doing four different hole patterns sometimes in the front we go for 28 holes, and in the rear 32. But it all depends on the rider, or even the fork, so like Fox 40 is really stiff, so you might choose to have a more compliant wheel for a stiffer fork and the opposite with a less stiff fork. It's just about trying to find the right balance.

What are the things that people should do if they are going to build their own wheels at home or even just maintain them?

Pay attention to the spoke tension. The biggest thing is that you have equal tension all the way around, that's the main goal and that will make sure the wheel will last as long as possible.

Do you see a lot of the teams pulling seals out of hubs?

I think it's a mental thing to have to a degree. I mean, maybe on track racing it will make a big difference but not so much in downhill. When you're running something like an Assegai or Magic Mary that's going to be creating more rolling resistance than anything the hubs seals will do. If it gives the riders a mental edge and makes them feel that they've got the fastest possible bike then I guess it works. I certainly wouldn't recommend it for consumers.

On these builds are we talking all brass nipples? Do you use any reinforcing washers or anything?

So with our rims we use aluminium DT Swiss torx head nipples and we fit washers as well. I also use the DT Swiss Proline Nipple Wrench for our nipples to tension them so that we don't round off the nipple itself.

Do you see a lot of mechanics changing the spoke tension depending on the track conditions? Do you see spoke tensions being slackened off?

Yes, but it's not something that the average rider is going to be able to do right because you need a truing stand and a trained mechanic, not to mention an expensive tension meter.

Is there a big variance between the tensions across the teams?

It depends on the rider but people have different tensions.

What are the biggest issues you guys see here at the World Cup?

Dents. We very rarely see a rim that's actually unrideable it's usually just dented and they'd rather replace it to make sure they get a better seal for the tire.


Mechanic: Jack Chapman

So you're riding the new DT Swiss rim out this year. How are you finding it?

So far, so good really. We've actually had a lot less casualties of rims than what we've ever had in previous years running the older wheels. So certainly better. No complaints here. So far at this race we have had no issues with rims.

So when you build up a wheel, does it differ from track to track?

No, not really. We've found sometimes, or one of our riders just complained a bit, about the wheel feeling too stiff in these open turns, like especially at the top. Like on the flatter turns where they're not super bike-parky, the wheels feel a bit stiff, like they're skittish. So we've slackened the spoke tension off a bit and that seems to have improved it. Not a drastic amount, it's not like a huge change, but that seems to have done the trick. I feel like, I've obviously not seen the track, but like Mont-Sainte-Anne for example, that might be something you look at there. Like when you're sort of off camber on a ski piece that has harsh impacts, just to give the wheel that little bit more compliance and hopefully a bit more traction.

What's the biggest issue you see with wheels at the World Cup? I mean, is it normally just getting smashed into rocks?

Yeah mainly, like, we've actually found that this year we've only ever had a puncture due to something actually cutting the tire in extreme cases. We've never actually had a rim so badly damaged that the tires gone down. It's always been, they've obviously hit such a square edge, it's cut the tire as well as broken the rim, just unavoidable. So yeah, really, I guess the biggest concern would be that that would happen but like I said, it's never actually happened so far.

Any top tips for people when they're building up wheels?

If you don't know what you're doing, get someone that does. I would say the main thing with a rim is not to worry too much about how straight it is, obviously that's within reason, you don't want to be all over the place. The main thing for a strong wheel is even tension. So if you find that you're having to make the spokes not evenly tension at all to get a straight rim then your rim's had it and it's done. The main focus is rather than worrying too much about a straight rim, especially on a mountain bike, worry about how evenly tensioned everything is because then ultimately that's going to be as strong as it can be.

Oh one more thing, tubeless top tips. The most common thing I see, not at a World Cup but from customers bikes, are people complaining their tires won't go tubeless and the sealant coming out the spoke nipples. It's because they have punctured the rim tape with tire levers. Most common thing. So when you put a tire on, that's tubeless, don't lift the tire lever all the way up vertical, try and like lever it on halfway and go little steps around the wheel as you go.

Tape wise are you just running normal tape? You haven't done anything funky in there?

Nothing funky no, we just got the standard rim tape, DT rim tape.

No silicone in the bead?

No, we're not gluing them on, like I said we've had no issues with punctures.

You guys use alloy, is this a conscious decision to use alloy rather than carbon?

Yeah, we've been running these and they've been fine. We've not had any issues with them not getting down and weights not an issue. If it's not broke, don't fix it.


Rider: Ronan Dunne

I see you're on DTs Ronan. How do you find them? Do you like an aluminium wheel?

Yeah so I've never for one ridden carbon wheels but our bikes are full carbon fibre so it makes sense for an alloy to just get that flex and even going into like loosing up the spoke tension to get you more flex and working with that kind of stuff is super cool. Yeah, with DT Swiss, this is our first year on the team properly with them and it's a game changer. Like I used to be known as a wheel killer, I think one day in Val di Sole I broke eight wheels back to back and two in one go. So yeah, like I was missing out on results just due to punctures. It was getting pretty frustrating and worrying as well. But this year, I haven't actually had a puncture on any race run and even on practice days I rarely get punctures. Even when you're at home training you don't have to worry about breaking wheels and ringing up the team so yeah, definitely a game-changer.

The whole spoke tension thing, do you make any changes or just leave it to a mechanic?

I leave it to the mechanic and depending on the track. Now if it's a real wet track we definitely use an upper spoke tension and just get that little bit more grip or just depending how you're feeling but no not crazy man as long as it's strong. We'll go for stronger over like traction radius. Yeah, we really haven't been having much problems this year at all, which is great.

Tubeless wise you always run tubeless, you're not running inserts?

So yeah tubeless for sure, no inserts. So this is the first year I've just given up on the whole inserts. Like last year definitely just ran them because like why not, but then I found even if you get a small flat spot sometimes the insert stops the sealant from getting out, so it's a mixed bottle like if I'm having a bad week punctures I'll just be like I would throw an insert in but luckily that hasn't been happening so just no inserts.

Have you got any top tips for people back home for looking after wheels?

Yeah, I'd say tire pressures for sure and then just keeping an eye on spoke tension. So like if you do ride just quickly fiddle through and then instead of having a loose spoke and being like "oh, that'd be grand" or missing a spoke, like that's one thing we've done every run, check to spoke tension. So you start breaking them when you start doing your own thing and not checking them. Yeah, just get your tire pressures right and check the spoke tension, and you should be good to ride around from there.