Pacenti SL25: Goldilocks Width
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Pacenti may not be a name on the tip of many roadie’s or gravel rider’s tongues, but it should be. Kirk Pacenti has been in the vanguard of MTB design for many years – pioneering both the 650b wheel size and the wide rim movement. With roadies getting dirty and bikes like the Open U.P. benefitting from 650b compatibility, his innovation matters.
The Pacenti SL25 rim is a 700c 6061-T6 alloy rim that is 26mm deep and 24.5mm wide. The internal width is a massive 20mm. For reference 15mm and even 13mm internal widths are still widely used. There are standards set out by a European organization, ETRTO, for tire and rim mating and according to its chart no tire smaller than a 28mm should be used on a rim with this internal width. While we have not ridden the rim with a 25mm tire we would happily do so, in our experience the standards are incredibly conservative as they likely know people will always push the envelope. Kirk himself suggests a 25mm tire for pure road riding with the SL25 and reports even 23mm tires have been run with no issues on the rim.
At 35psi our set of 33mm Maxxis Speed Terrane tubeless tires measured 35mm on the nose, so be aware of that if you’re lining up at the UCI ‘cross world championships. We got these in for gravel and adventure, so the extra volume is very welcome. A wider tire creates a wider, more circular contact patch, and the wider Pacenti rim amplifies this, which all adds up to confidence. The SL25 is disc specific and tubeless friendly while each rim weighs only 450grams, meaning you can build up a very light set of back road adventure wheels for an amazing price. A rim brake version called the SL23 is also available with almost identical dimensions.
Ergott Wheels, a long time Pacenti collaborator out of New York, built these SL25s up with White Industries CLD hubs – 28 hole front and rear – and Sapim Race spokes. The front hub weighs 145grams while the rear hits 265grams. These wheels were built for our adventure rig, a custom Seven Mudhoney SL with dual QR and TRP Hy/Rd disc brakes. While Ergott currently makes all Pacenti’s made-to-order wheels, Kirk plans to offer complete wheels very soon. He’s working on a disc version of his own hub and is waiting to see where the spacing and axle standards land before offering complete sets.
Setting these wheels up tubeless was one of the easiest tubeless set-ups we have ever experienced. Undoubtedly the Maxxis Speed Terrane tires played a big part in this, but the tire went on the rim by hand. Yes, by hand! No tire levers breaking, no cursing, no banged knuckles. They sealed first try with a Lezyne Pressure Overdrive and 45ml of Orange Seal. We set aside an hour to get the job done. It took 15minutes.
After weeks of bashing these wheels down trails no rigid adventure bike has any business being on – single track, loose chunky rock, blazing fast jeep track descents – the wheels have proven bulletproof despite bottoming the rim out countless times at absurdly low pressures. The biggest benefit of the Pacenti SL25 rim’s width in our mind is what it does for the tire. You can run a narrower, lighter tire and it will give you the contact patch and volume of a wider, heavier tire on a narrower rim. That means it’s livelier going up hill, more nimble on the ’cross course, yet just as capable at handling nasty surfaces and providing big comfort. We also found the Maxxis Speed Terrane’s very specific hard pack focus was expanded considerably thanks to the SL25. The low file style tread on the tire’s center keeps it rolling incredibly quickly, but thanks to the wide rim, the larger nobs on the shoulders work better on the SL25 than narrower rims. The circular contact patch allows them to hit the trail sooner and deform more completely to match trail contours for much improved traction. When reaching for any new gravel or adventure wheel, we’ll be looking for a 20mm internal width – the Goldilocks width. It’s just right.
Price: $109 per rim; pacenticycledesign.com
To get a set built for yourself; ergottwheels.com