Open U.P. sizing (right in between M/L)

5’10 and typically ride 56 in Specialized (Venge) and Large in Santa Cruz (Blur XC) – both my fitter and even OPEN support seemed a bit stumped on what size I should get, since I’m pretty squarely in between sizes based on my Venge fit (perfect fit).

Any recommendations on how I should think about sizing? This is my first gravel purchase and I’m tempted to go a bit smaller since I want this to be my gravel race bike, but not sure about toe clip given bigger tires, and if most people size a bit up similar to MTBs.

I’m 5’9 and ride a 54 Tarmac, and have been very happy in my size M U.P. I don’t feel like I’m near the edge of the size range there.

Perhaps the OP has long limbs?
I know I do and even though I am only 1.78 m (roughly the same as the OP) I definitely need size 56 or L. Since the OP was at a bike fitter, I reckon this has all been x-ed out.

I’d probably tend to L — that’s the size you know works. I haven’t tried the Open UP, but I have tried two other of Gerard Vroomen’s bikes in M, the Exploro and the Strada. Both are too small in M for me. I reckon the Open UP is sized similarly. Like your Venge, my current road bike is in size 56 cm and the size is perfect for me. I had three bike fits up until now, so I know the size is dialed in. Consequently, I put in an order for the Strada earlier this month, size L. Woot!

I am usually always in for a smaller frame. However, on a gravel bike, larger frame with short stem is the way to go


As a very general rule, if you’re stuck between two sizes, I recommend sizing down. It’s easy to make a small bike a bit bigger than a big bike a bit smaller.

However, in your case specifically, it depends on the kind of riding you’ll use the bike for. Try and gauge for yourself how similar you want the new bike to be to your current position. Low and fast? More upright and comfortable?

Sizing down between disciplines is a pretty old school way of thinking, since manufacturers have already thought about that and accommodated it in their geometries. But this is obviously highly variable when you’re comparing bikes from different manufacturers, so you’re doing the right thing looking at the individual geometry charts.

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Thank you all! I believe my limbs are a bit on the longer side (hence why I was able to fit my Large MTB SC blur comfortably) – based on your feedback so far, I think I’ll go with a large, given I live in the Bay Area this bike will be 20% gravel/dirt, 80% tarmac, but even so, I think having a bit more comfortable ride will be worth the slight road performance trade off.

Also did some measurements per suggestion – not sure if these help any, but sounds like I should go with a Large

140mm Stem
30mm spacers underneath
30inch inseam

On my super six evo 2013 (similar geometry as venge) I have a 150mm stem

140 mm stem? Yes, I’d definitely go for large then. (It sounds as if you have very long arms.)

Typically when you are between sizes that mean you can adjust by either going for a smaller stem on a larger frame or vice versa. But there is nothing much longer than 140 mm, and even a 140 mm will impact handling negatively. Of course, even adjusting stems, you will sit more aggressively on a smaller frame, because you saddle needs to be raised more. Also this is probably not desirable on a gravel/all-road bike.

thank you @OreoCookie !

You might need to look at an XL. If you’re on a 56cm Venge with 30mm of spacers and a long stem, you’re a size too small to start with. You should be on 10mm of spacers on a bike like that. I think the aerofly handlebars are shorter set of bars too. You’re a L easy.

Venge: 555 Stack + 30mm spacers + whatever angles.
398 reach + 140mm stem + 80mm reach bars

Open Up L: 580mm Stack + 10mm top cap(?) + whatever angles
387mm Reach + ?? Stem + Reach

You might want to consider the Cervelo, which is shortly longer
Aspero 56: 580mm Stack + 10mm top cap(?) + whatever angles
397mm Reach + ?? Stem + Reach

Normally gravel, you’re +10mm and +10mm

+1 to this.

Also, I think you’re best bet is to measure the stack and reach of your best fitting bike and then find the U.P. frame that most approximates it. It the frame you buy is a touch small, spacers and a longer stem are always better to add than subtract to achieve ideal fit, in my experience.

Thank you for the detailed response! One follow-up question I have is if my flexibility on the bike improve, will that have any impact on how stack / reach works out? Or will it make the problem even worse where I’ll have to get even longer stem.

I admittedly took 7 years off the bike and just started riding again this past year. Been working through getting back my flexibility / getting lower on the bike.

You’ve already got an insanely low fit for general riding. You’re in a setup that would be limited to folks who can touch knuckles to the floor, have great core strength, and have ripped abs. Do you use the drops right now?

basically… you’re ‘outside of the box’ on your fit. You’re either built weird, comfortable in an odd position, or you might want to try a few things before getting that next bike. The long stem on a longer-reach bike seems the most odd - the venge is about 10-15mm longer than normal and your stem is 20-30mm longer which is a big difference. When you look down at your front tire in your normal riding position, your bars should be about right over your front wheels hub (you shouldn’t see the hub). Is that about right?

Hey I’m an idiot, measured the stem incorrectly (did the whole length rather than from center bolt to headset cap.

I actually have a 100mm stem. Some other stats below:

Reach (saddle tip to center of bars): 58.7
Drop (top of saddle to bar tops): 7.0
Seat angle: -2
Saddle height from BB: 73.0 (BB up to the center of top of saddle)
Saddle height from 6 o’clock bottom of the crank: 88.5 (axel of pedal,up to the center of top of saddle)
Saddle measurements: 2.5 (measures from flat rails - front to back - measured from the non drive side)
Tip of saddle to center of steer tube/top of stem: 49.0
Tip of saddle to brake levers: 73.7
Bar angle: 13 (degree-measured from the bottom angle-drops)
Handlebar drop: 130
Handlebar reach: 80
Stem Size: 100
Stem Angle: -6
Bottom of handle bars to the bottom of fork (drop outs): 55.0
Head Tube length: 150
Spacers: 40 (from headtube to bottom of stem-includes top cap)

Oh, ok. Typically, 56 cm frames come with 110 mm stems, so 100 mm is a tad shorter, but fully within range. I’d still say 56 cm/L is the better size for you. If you go for 54 cm/M, you will probably be at the outer range of what the frame can accommodate, perhaps extending beyond that.

Since we are roughly similarly sized (on- and off-the-bike), I have a 110 mm stem on my 56 cm frame. None of the 54 cm frames (of various make and models) did not fit me, and they did not fit me by a wide margin. I had to pass a lot of opportunities of getting great bikes for a bargain. Perhaps I could have made it work with an extreme stem, say, 140 mm — I did not try that. Why bother if the default stem length for 56 cm seems to work.

100mm is about right then.

Some measuring tips above for when you’re buying or renting a bike.
-Saddles are different lengths. In my experience, your tailbone usually is consistently at the very rearward point of any saddle, so that is a better measurement for fore/aft.
-Saddle-middle is not helpful.
-A lot of the 3D measurement with a tape measure is unreliable bike-to-bike.
-Saddle tilt varies saddle to saddle. I like to take a measurement from the rails below the saddle as it is easier to get a good number.

That saddle height measurement is at least 15mm off. You measure from the Bottom bracket center to the top of the saddle inline with the post center. I’d say more. I’m guessing you measured the outside of the shell, which would put you close to 20mm off - so about 750mm (29.5 in). You gave a measure from the pedal, which backs up your 720, but this number seems an inch (~25mm) too low. This measurement is critical on a traditional frame, but these have a lot more space and you’re probably within the seat post range.

Those bar measurements seem off and bar measurement are generally wrong on the mfg’s website anyway (or they lie).

In any case, L is the way to go with a 110 Stem for the same fit. If you’re going to use this for light off road, you’ll want the bars a bit closer and higher to accommodate ‘arm suspension’.

Thank you @jfranci3 this is super helpful – I actually test rode both M and L, and decided to go with M at the end based on my improved flexibility (hence ability to go lower) and overall feel on the road.

Re-measured the saddle from BB to double check, ended up being 735

This said, which stem length would you recommend for an M size frame assuming a slightly more aggressive / aero fit than the current set up.

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I’d get a bunch of random stems and try them all. I’ve got a shoe box ‘o stems that get me passed around here.

Are you ordering a frame? If you need a random one to start with - 120mm. Otherwise roll with the one they give you for a bit.
BTW- My favorite stem is the $40 Syncros (Scott) RR2.0 or 1.5 they’re basically the same thing. Cheap, super clean looking, on the lighter end of the scale. One problem, the Syncros garmin mount doesn’t have a light attachment.

I was in a similar situation and was able to demo both sizes and the fit was very clear. I ride a 54cm tarmac end usually end up with size large mountain bikes. I chose to go with the M Open UP and have been riding it for 3 years with no issues. Would highly recommend a demo and also reaching out to the guys at OPEN. They are a class act and open to helping you any way possible.