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Profile’s 38 Twenty-four Carbon Clinchers

Profile has been in the bike business for decades. They are well known for their aero bars and triathlon-specific items, but they are quite new to the wheel game. In 2013 Profile released a pair of new-school wide-rim wheels: the tri/TT-specific 78 and the more road-oriented 58. The subject of this review is the newest member of the twenty-four family, the 38.

Profile has gone for a very functional naming system. All three twenty-four series wheels have a 24mm-wide carbon rim, while the rim depths are (not surprisingly) 78, 58 and 38mm deep respectively. There are actually five models when you consider that each is available as a carbon clincher and the deeper two are also available for singles as well. All wheels sport Sapim CX-Ray straight pull spokes, Profile hubs (11-speed compatible in the rear of course) and very slick QR skewers. Included in the package for the 38 wheels was also a set of tyre levers, a spacer for 10-speed cassettes, several spare spokes, a tool to keep the spoke from winding up when in the trueing stand, rim tapes and a set of bright red brake pads designed to work with the Profile braking surface.

Initial impressions were very good. Aesthetics are a very personal thing, but these wheels have minimalist labelling that is unlikely to offend anyone (though I know some riders who like more in-your-face looks). Black hubs, spokes and rims looked really sharp on my mostly black bike with a pair of black tyres mounted. I put 25mm tyres on for the review and they looked like just the right size to complement the rim width. The freehub body is quite modest in its freewheeling noises. The hubs feel silky smooth.

A quick comparison against advertised competitors’ wheels reveals that the twenty-four wheels are right in the mix. Weight is neither notably light nor markedly hefty; 689g front and 855g rear, given the lower price of the Profile wheels (at $2400 they are considerably less expensive than many alternatives) I expected them to be heavier than the more expensive wheels out there. Rim shape is also comparable (to the eyeball test anyway) to other choices. The rims are wide and the inner edge is blunt, just like most other current rims.

But how do they ride?

On-paper specifications are one thing but the proof is in the riding, otherwise why would we try out new gear and why would you read about it? My own wheels are skinny, shallow and aluminium. These Profile wheels are almost the same weight, yet they gave the impression of being lighter in back-to-back riding. I felt like efforts to accelerate were met with a faster response. Not once did I notice the rim depth in crosswinds.

Knowing I had to go back to my narrow rims after the test I did not readjust my brakes to accommodate the wide rims, I simply used the quick release adjuster on the callipers to open the pads apart. As a result there was barely a paper-thin gap between the pad and the rim with the 38s. I never detected rubbing between rim and pad – these wheels are laterally stiff.

I was able to drop the air pressure in my tyres from 120 psi (with 23mm tyres on skinny rims) to 100 psi (25mm tyres on fat rims) and did not get a pinch flat during the test period. I wouldn’t say this combination was more comfortable (I expected it might be) but rims almost twice the depth I was used to have much higher radial stiffness, so the fact that it was about the same is a good thing. I did notice that on chip seal roads the usual buzz in the bars was absent. Whether that is the carbon in the rims or the lower pressure in the tyres doesn’t matter – it was a welcome change.

Are carbon clinchers safe?

If you’ve read internet forum threads about carbon clinchers, there are quite a few horror stories about exploding rims and the like. With an alloy rim, most of the heat from braking goes into the metal rim which then releases that heat to the air (and yet on a tandem, for example, the tyre can still blow off the rim under braking). With a carbon rim, the carbon is a great insulator so all the heat goes into the brake pads (and what heat goes into the rim stays in the brake track). Every carbon part has a glass-transition temperature – the point at which the resin reverts to a liquid. The pressure of the tyre will cause the rims to bulge apart once the resin liquefies. At best you’ll feel a pulsing in the brakes and at worst the tyre will blow off the rim leaving you riding on a broken carbon rim.

I think carbon clinchers have come of age with the move to wide rims and the development of high-temperature resins. The wide rim means that even a tall guy like me can ride the wheel without worrying about a pinch flat (the Profile rim is rated for 125psi which is more than enough given the width). The high temperature resin and special brake pads means that the rim is unlikely to ever hit the transition temperature.

What about the brakes?

The first time I rode on carbon rims was on my own TT bike about twenty years ago. In the dry the braking was OK, but it was accompanied by a virtual burning up of the brake pad – you could smell the stink. In the damp or wet, well it was a great thing that I didn’t ride the TT bike in the wet much because there wasn’t much slowing down going on. In stark contrast, the Profile rims with the Profile pads were excellent. I did notice that they were a bit grabby at really low speeds, but above 15kph they worked just as well as my usual braking. I even had the chance to ride them in the rain and there was no real difference – a huge improvement on where carbon rims were not that long ago.

All indications are that the pads wear out really quickly. While the review wasn’t long enough to measure such things, I did notice a large amount of red dust on the fork crown after every ride. A red line also appeared on the braking surface of the rims. All this red stuff just wipes off, but the quantity of it suggests that the pads are not going to last that long. If that is the cost of decent braking, then I’d happily cover it. Also, if these red pads help ensure that the transition temperature is never reached I would not be tempted to try another brand of pad.

I wanted a second opinion on the wheels, so I leant them to a friendly bike shop owner who regularly rides on carbon clincher rims. His experience was quite different than mine with braking – he got a lot of squealing and worried that he might not slow down in an emergency. This was the same wheels, tyres and pads so the only thing I can think of is that the way in which the pads hit the rim must be an important factor in getting good braking from these wheels. In all other regards his opinion on the wheels matched my own.

The wheel ‘package’

At most of the races I have participated in over the last decade I have been in the minority of riders by running alloy rims. For a long time I have had carbon wheel envy! Not wanting to run singles and not willing to risk skinny carbon clinchers I didn’t have much choice until the plethora of wide rim carbon clinchers recently came to market. In looking at the whole package (yes the rim defines the wheel, but it is the whole wheel you have to live with) the Profile 38 is an excellent option. Competitive weight, good braking, ‘fast’ to ride on, comes with everything you need to get going and all at a lower price – what’s not to like? 

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