Huge MTB faster than racy gravel?

[Bio_Carbon]

I'm currently not able to ride, due to an "accident" (for lack of better word), but I keep thinking about something I experienced some years ago. I'm a fairly "new" cyclist. Lots of friends been riding bikes, so I wanted a piece of that. In September 2019 (lucky... not knowing what hell would break loose and how hard bikes would be to come by) I got myself the next year's, 2020 model of the Trek Roscoe 8. Huge bike. Enormously wide 27.5+ tires, wich on smooth roads make a "wrrrrrrr" sound. Anyhow. I liked it a lot, I commuted with it, I barreled down forest trails on it, went shopping with it, committed crimes with it. In 2021, I felt like treating myself. By then I was a good deal fitter and figured I'd like something that's a little more like a fast road bike, but something that could still put up with some gravel, as a short ~1km gravel stretch is part of my normal commute. So I tracked down a Bianchi Impulso Allroad (GRX 810 11sp) two countries over. I've put it together myself, had it inspected at a very respectable shop in the inner city specializing in road bikes - classic and new. The boss was excited, I was happy. Everything seemed fine but I noticed: On average I was a little slower than on my mountain bike. Probably about 3 kph on average. Rarely ever dropped below 20kph average, sometimes in good weather, I'd even scratch 25kph, now I was in the lower 20s or even slightly below that. But why?

How come that my enormous, heavy, 1,500€ MTB, with dummy thicc tires, is considerably quicker than this sleek, Italian 2,500€ 2x11 speed? I got lots of compliments, but I'd rather have taken a couple kph+ on my average. To this day I don't know what happened. I liked it, but for that reason I usually ended up just using the Trek. Anyone got any clues?

Specs sheets for both:

https://www.vitalmtb.com/product/guide/Bikes,3/Trek/Roscoe-8,27085

https://www.serviziocorsa.com/en/Bianchi-impulso-allroad-grx810-11sp-hydr-disc-2021

 

[fossyant]

You've done something wrong. On tame stuff the gravel bike will be way faster, by a fair margin (or should be). My cyclo cross bike (bit racier and an older vintage) is way faster than my FS MTB, but a lot is down to tyres and bike weight. 2.3" Maxxis Minions for grip, vs some light 38c gravel tyres.

What tyres are you running ?

Are you sure it's set up right bike fit wise ?

 

[N0bodyOfTheGoat]

Change in fitness and MTB tyres/tubes had lower rolling resistance?

I often hit 40mph+ downhill these days on my gravel ebike compared to when I was fitter on my road bike, that will be the extra ~30Kg!

 

[ColinJ]

Your brakes might have been rubbing?

A friend had the same problem [rear brake knocked when carrying bike in the car, and then rubbing on rim] on the Manchester 100 sportive one year. He only spotted the problem after tiring himself out chasing me for 55 miles and then grovelled back for 45 miles.

If it really did feel like that (when riding fairly slowly on a level road) I would check that your brakes are not rubbing. I did a 200 km audax ride once which half killed me. When I got to the finish I discovered that my rear brake had been rubbing the whole time!

Lift the front wheel off the ground and give it a spin. It should spin lots of times before it stops. Repeat with the rear wheel.

When I tried spinning my rear wheel after my audax ride, it only rotated about 1/10th of a turn before stopping.

Another problem that I had/caused - an overtightened quick release!

That's too tight - I learned that after one exhausting ride during which I couldn't figure out why my bike felt so sluggish. I checked my brakes and they were not rubbing. It turned out that excess QR closing force was squeezing the wheel bearings and causing a ridiculous amount of friction.

 

[Drago]

My gravel machine is obscenely quick. I really don't know how they managed it, but its nigh on as quick, while somehow requiring less effort, than my road bike.

I've ridden a few tarmac terrorists over the years (MTBs modded for urban use) and while they can be quick were talking a different class with the way some of these gravel machines shift.

More likely theres a reason your gravel machine isn't performing optimally rather than you suddenly discovering some new field of physics with your MTB.

 

[Sharky]

Are we on the same route and weather conditions?

The only way to determine is to do a fixed out and back route of about 10 miles on each of the bikes, riding "tempo". At a pace you can maintain, but just under your threshold.

If you had a power meter, you could ride the route at a fixed power output. Could also use a heart monitor and keep to a certain heart rate.

Good luck

 

[Rusty Nails]

Perhaps you just have a bit more confidence or just feel more familiar with/comfortable riding a flat bar bike.

 

[fossyant]

Perhaps you just have a bit more confidence or just feel more familiar with/comfortable riding a flat bar bike.

That's a big factor as you feel everything on a road/gravel bike. The gravel model isn't on big tyres, so should be quick, but they are Kenda's.

 

[ColinJ]

Your brakes might have been rubbing?

I just looked the bike up - disc brakes, so knocked rim brakes not the issue, but I have suffered disc brakes dragging as well!

...

Another problem that I had/caused - an overtightened quick release!

But this bike doesn't have QR's so definitely not that!

 

[Webbo2]

I wonder if the times and distance were recorded on the same unit

 

[ColinJ]

I wonder if the times and distance were recorded on the same unit

Aha, that gives me an idea...

Metric units (km) used on the MTB but gps accidentally reset to imperial units (miles) for the Bianchi?!