I've recently got an iPhone as my work phone so have been messing about with one of the GPS tracking apps (MotionX) on it. On the last two weekends, in pretty similar ground conditions, I rode the same 13 mile local loop, with a fair bit of climbing and some decent downhill sections, on two different bikes – this Sunday on my Epic and last Sunday on my Enduro. The Enduro (with coil shock and coil Pikes) is bound to be a good bit over 30lb and the Epic (with SID's, XTR, carbon and American Classics) is under 25lb – wouldn't surprise me if the Epic is 8lbs lighter.

Now I've read threads on here in the past that say bike weight doesn't make that much difference but in my case the Epic was over 12 minutes faster. That was despite more difficult weather conditions (hot and very humid) and a few minutes lost on the Epic getting myself sorted out after an off. Stops etc. would have been similar – perhaps slightly longer on the Epic as I chatted to another rider for a couple of minutes, and early on stopped to take a layer off. Possibly due to the weather I actually felt stronger when riding the Enduro.

I was expecting there to be some difference but nothing like that. So how much of that is likely to be down to weight and how much to other factors like geometry or gearing etc?

Depends on the weight.

There will be a range of normality and then small bits outside the bell curve.

Ride my commuter-it weighs a ton. But at 28lbs fully laden against my 21 lbs mtb well you will notice it.

But if it was 28 and 26lbs maybe not as much? Want to get detailed? get your statistics out books out.

Tyre choice and bike set up could account for that. I'm sure the weight would make a little difference but not that much. Try strapping 8lbs to the Epic frame and then time the route, I bet it's still faster than the Enduro.

I was expecting there to be some difference but nothing like that. So how much of that is likely to be down to weight and how much to other factors like geometry or gearing etc?

weight – a little. Geometry and gearing – nothing.

Real factors like hydration, fatigue, blood sugar etc – most of it.

My race bike is always faster. Because it is lighter and has light wheels and a position that is more efficient for my legs.

I'd gor for tyres as a key variable as well as tyre pressure

Possibly losses in the suspension

I don't think mass is that big a deal once we include you

Oh and how aerodynmamic you and the bike are

A minute a mile difference is huge. What were the 2 times?

If you lose 2lb off the bike you'll have a much bigger improvement than 2lb off yourself.

How does position affect your legs luke?

Edit and how does your later post work?

The Epic has Speed King Supersonics on and the Enduro has Eskars. The Epic was also marginally hit the fastest top speed as well, but I think that was down to there being a fairly smooth bit on one of the downhills as I'm pretty sure the Enduro was faster on the downhill stuff.

Real factors like hydration, fatigue, blood sugar etc – most of it.

Possibly, although I felt like I was struggling more on the Epic due to the humidity etc. Two rides isn't really a scientific example anyway but given it's my most common loop I'll see if the difference continues and also how my other bikes (both hardtails) compare as well.

I'm not quick(!) so the times were 2:08 on the Enduro and 1:56 on the Epic. That's door to door, including all stops etc. If I hadn't crashed near the end of the ride on the Epic then the difference would certainly have been well over 15 minutes.

I run the Supersonics on the Epic at 50psi and the Eskars would have been at 30-35psi.

The 2nd post is pure me n'tree knowledge. Cos he's a bifter and because I'm no faster when I lose weight.

Leg position- like time triallers. Getting more vertical to the BB gives you a more powerful downstroke, which is why they run their seatposts at -10mm layback and have 78 degree seat angles. There's also something about having your legs at 90 degrees to your body, but I don't know the whole of that.

Ah, as scientific as I thought.

Bow come only tters use this knowledge. Someone ought to tell lance.

Leg position- like time triallers. Getting more vertical to the BB gives you a more powerful downstroke, which is why they run their seatposts at -10mm layback and have 78 degree seat angles.

No it's not. It's so they can get a lower flatter back whilst maintaining the same hip angle. Your position over the BB has little real effect on power output.

yup it's true. I am significantly faster round w2 on my 26lb hardtail verus my 34lb 'big' bike. However when I finish on the full susser I don't feel like my fillings have been shaken out!

I mostly ride the full sus these days when out with my less fit weekend warrior mates 🙂

They do use it, but to a lesser degree, because riding a TT position for 4 hours would make you sore.

I know weight's not all of it (which is why my Anthem is faster than my Scale) but I reckon, from personal experience, bike weight then tyres is most important.

You do come across as a total fluffy bunny on this channel by the way 😉

Bike set-up:

Both bikes are set-up exactly the same length from tip of the saddle to the top of the stem bolt, but the Epic has a 90mm stem and the Enduro 70mm. Stood side-by-side the saddle on the Enduro is several inches taller than the Epic although I'd expect it sags a good bit more.

yup it's true. I am significantly faster round w2 on my 26lb hardtail verus my 34lb 'big' bike. However when I finish on the full susser I don't feel like my fillings have been shaken out!

The Epic is the best of both worlds! It feels faster than my Zion, which is a bit lighter than the Epic, but it'll be interesting to see if that's proven against the clock!

Personally if you are looking at total times, the extra speed on the ups & flats on my light hardtail far outweighs the few seconds faster I am on the downs on a suspended bike. I have more fun on the susser though – not all about how fast you get round !

yeah but which was more fun?

fwiw tyres make a big difference ime

Luke how do you know which bike is faster?

You do come across as a total fluffy bunny on this channel by the way

I think many of us come across diferently to real life, you included! 😀

yeah but which was more fun?

Tough call – both good fun but the Enduro has definitely improved my riding. I tend to try things on it that I don't on the other bikes, then once I've sucessfully cleared them on it I give them a go on the other bikes – and usually make it on those too.

riding a TT position for 4 hours would make you sore.

Maybe. It takes a bit of training to get my neck used to the strain of the angle I hold my head at, but apart from that I've done several ~100 mile rides on my TT bike with only a minor increase in handlebar height, and I've not felt worse afterwards than I would have after a similar distance at a similar intensity on a normal bike.

I run the Supersonics on the Epic at 50psi and the Eskars would have been at 30-35psi.

THAT is your key difference… Wouldn't be surprised if you were even quicker on the Epic than 12 minutes difference, given that the contis are very fast tyres and the Eskars are big heavy and draggy by comparison.

Why do you think the xc racerboys all run skinny fast rolling tyres pumped up quite firm, even if they don't grip that well! Cos it's faster innit…

Finally got round to weighing the Enduro and it's 32.8lbs, which is slightly lighter than I'd expected.

That's almost 10lb lighter than my fastest mountainbike 😉
and got a 37lb old skool enduro SX (around the same age as yours) that can almost keep up with it.

I agree, it's almost all down to tyres/wheels, switch wheels and you'd be as quick/slow on either bike

MBOY you'll find most of the world cup XC riders are using wider tyres now tubeless with pressures down to between 25psi – 30psi as off road it's much faster with better grip . Schwalbe have a link on there site to a study about rolling resistance which explanes it all

I rode the same loop again this morning, on a 23.1 lb hardtail fitted with the Epics wheels and tyres. The time was 2:02, which is exactly halfway between the Epic (which is just short of 2 lbs heavier) and the Enduro (which is almost bang on 10 lbs heavier).

Until I got home and checked the GPS I thought it was going to be a fair bit quicker than the Epic as I thought I'd stopped a bit less, didn't crash this time, and while descending was definitely a little bit slower I didn't expect it to make much difference overall. An analysis of the GPX tracks though showed the Epic as gaining a minute on the climbs, losing a minute on the flat (which was about 50% of the total ride time) and gaining nearly 6 minutes in the descents (just under 32 minutes compared to 37.5 minutes).

MBOY you'll find most of the world cup XC riders are using wider tyres now tubeless with pressures down to between 25psi – 30psi as off road it's much faster with better grip

Yeah, but these "wider" tyres are hardly massive are they, and they're certainly not heavy or have thick sidewalls! They might be a bit wider and lower pressure, but they're still very light, and have a very fast tread pattern.

I rode the same loop again this morning, on a 23.1 lb hardtail fitted with the Epics wheels and tyres. The time was 2:02, which is exactly halfway between the Epic (which is just short of 2 lbs heavier) and the Enduro (which is almost bang on 10 lbs heavier).

You'll probably find quite simply cos the Epic beats you up less than the hardtail would, you're able to pedal it harder for longer. Fit the wheels off the Enduro for an experiment, then go ride, I bet you'll be approximately 2 minutes slower on the hardtail with the Enduro's wheels as you were on the Enduro!

FWIW, I changed my hardtail from 3x 9 to singlespeed, and did a local loop a few times – always 10-15% shorter time. So geometry pretty similar; wheels / tyres etc the same; a bit lighter; but ss forces me more I guess