Lets assume we have 2 bikes the same model, same tyres.

1 is carbon and built light, lets say 9kg for example… it has lightweight wheels, lightweight gears, carbon frame, bars, post etc.

The 2nd bike is the exact same shape, geometry, travel etc. Same model but Alu version, along with same forks for arguments sake, but built at a weight of 11kg due to wheels, cassette, cranks, etc all being a couple of versions lower spec.

Over a 1 hour ride at pace (or a race for example) how much difference would you think we’d see ?

I weigh 90Kg+ kit. So from 99Kg to 101kg = 2%.

Aka nowt!

the lighter bike will accelerate slightly quicker but once upto speed the differences are probably non existent (assuming there are no hills)

Don’t think you can quantify it in time. Its down to the amount of effort needed to propel that weight around for 1 hour. The rider on the lighter bike will expend less energy for the same ride at the same pace.

Is this road or MTB?

I think weight is key for road as its more based on power to weigh ratios.

Ascending and XC on the MTB is very similiar to road so I would say weight would impact it. Descending I think weight helps, I think Chris Porter formerly of Mojo was doing testing recently where he was adding weight to bikes as it made them more stable at speed and helped maintain this speed.

The discussion is for MTB.

Specificially from my POV it’s for MTB racing… So fatigue only plays a factor in the context of the rider being able to go harder at the end, not a question of how tired the rider is once they’ve finished.

The reason i’m asking of course is because i’m curious as to whether i should spend some money and buy an XC whippet bike for racing XC… Or just stick with my Parkwood/Whyte T130

You ride Zwift Weeksy??… w/kg aint it. Those 2 kilos will be added to your overall weight and need to be pushed up the hills. So slower up, possibly faster down, and negligible difference on the flats if all else is equal. But more energy overall will be used to move bike b than bike a.

On a heavier bike, particularly with heavier wheels, it’s only really noticeable when powering out of corners on twisty turny courses.  You need to put a bit more effort into the pedal strokes to accelerate the way you are expecting to, and you might need one more pedal stroke.  Over time, this adds to your fatigue.  So whilst the maths may say no when it comes to working against gravity, I think it does matter in your overall race times on a windy course.  Which most XC courses seem to be.

Same weight tyres having different rolling resistance? Trade off with grip etc, but all out speed might be affected

You ride Zwift Weeksy??… w/kg aint it. Those 2 kilos will be added to your overall weight and need to be pushed up the hills. So slower up, possibly faster down, and negligible difference on the flats if all else is equal. But more energy overall will be used to move bike b than bike a.

Different weight though isn’t it ? not just the overall weight of rider and bike as it’s sprung/unsprung, etc

In a Zwift context, 2kg doesn’t make much difference at all…. but i don’t think that 2kg Zwift weight is the same as 2kg bike weight.

I think weight is key for road as its more based on power to weigh ratios.

in the mountains it’s true, on the flat it’s all aero riding bikes 1 kilo over the limit.

How technically adept are you? Are you going to loose the time you’ve made up climbing when descending on a flighty steep angled xc race bike? I am increasingly begining to think that i need to make some weight conscessions to aid my inability to descend – in particular I think adding 300g to get a dropper post is probably worthhwile.

How technically adept are you? Are you going to loose the time you’ve made up climbing when descending on a flighty steep angled xc race bike? I am increasingly begining to think that i need to make some weight conscessions to aid my inability to descend – in particular I think adding 300g to get a dropper post is probably worthhwile.

I think the simplest answer to that is…. “i’m average”… This is where in particular the argument of any purchase falls down for me. If i race at Southern XC i would say expect to finish 30th out of 55….  (2017 results roughly). Lets say i was on a bike that was even 2 minutes quicker over the time/course… that may only push me up to 28th place. Or indeed a slower bike of 2 minutes may again, be 2 places down to 32nd…

My “should i buy…” all falls apart right about there… but doesn’t mean i’m not tempted.

In general, lighter will be faster, but that needs to be qualified a lot. “All other things being equal” is nonsense, they won’t be equal, some things will be different. The speed difference will depend a lot on the trail and the rider. On long, steady climbs, a 2 kg difference won’t make an enormous difference. On twisty XC pedaling sections, a lighter bike will probably accelerate better, but that will depend on the fitness of the rider. If it’s a very short race, acceleration out of corners might make a difference, but if it’s a long race, you will mostly be spinning along trying not to blow your heart rate up so a heavier bike with better handling might carry more speed out of the corners. A professional XC racer might be able to benefit from a superlight bike, but an average rider might not. If the descents are rough, bigger, grippier tyres will help, especially for average riders, on smoother descents, skinny lightweight tyres might be the way to go.

On top of that, slimming 2 kg off a bike’s weight costs serious money. That’s money you could use for something else, so you need to identify the most cost-effective way to go faster.

All things equal – then yes. But in the real world for us weekend warrior xc types, then I doubt it makes much difference as there are many other factors that impact on our race before a tiny amount of weight makes a difference.

Anyway, I have just done the swap from carbon (cracked it) to the old alu frame I had lying about. I reckon I will still be racing the same folk for 20-something place come the southern xcs.

Ferrals – yes, get a dropper. Mine has added 400g, (brand x external one) but it makes enough of a difference on a technical descent to make it worthwhile. Just feels safer too, so you don’t worry about drops and other tech features. My local trails seem to be getting a trail-pixie make-over too (yay!) so tech features are becoming more common on every ride now.

Have you included uphill and downhill differences? The heavier bike will roll faster downhill than the lighter bike. Likewise a heavier rider will too.

So another question: 2 riders of the same fitness and same bike tie in a race. One rider is 60kg and the other is 90kg. Now give them both a bike thats 2kg heavier on a course with a mixture of gradients. Who will win?

If you want a lighter bike, buy a lighter bike.

If you want to get faster at XC, from your current mid-pack, training and skills coaching will be a better investment.

I got a load faster on twisty wooded XC after some skills coaching with Jedi – I was able to carry more speed and corner much faster.

The reason i’m asking of course is because i’m curious as to whether i should spend some money and buy an XC whippet bike for racing XC

Spend what you want to spend, what are your goals? Fun or Podium? If it’s fun spend the cash on going to the races and some kit, if you want to go chasing the g and podium then find someone to sponsor you 😉

Does anyone really think that buying a new bike will make more difference than being really fit?  Daftest advice ever.

Who will win?

Depends on their power to weight ratios of course.

Spend what you want to spend, what are your goals? Fun or Podium? If it’s fun spend the cash on going to the races and some kit

My wants and my realistic goals are a million miles apart. i WANT to be a podium, but the simple fact is that whilst i’ve dropped 8kg off myself this year i’m still 10kg if not 20kg away from being a podium kind of guy. Sure, a heavy guy may podium, but he’s also a lot fitter/faster than me…

It’s all about the fun…. but i’m a bloke, so part of the fun comes from the battles…. If a lighter faster bike puts me in more battles for higher places, then that has the side-effect of being more fun.

Here’s one thing I will say, a lighter bike ‘feels’ faster, there is some science behind it whereby the body senses changes in acceleration more than changes in speed so a faster acelerating bike is going to ‘feel’ faster. So having a lighter bike means having more fun!

weeksy – do it. Sounds like you want the carbon xc bike anyway. Scratch that itch. I thought the same a while back and bought a 2nd hand dirty harry frame from here (you’ve seen it – the bright pink one). Loved the way it rode. It felt fast, if maybe only a tiny bit faster. A bit gutted when it cracked, but it’s had a decent run being 6 years or so old.

It’ll cost you a bunch of cash if you carry it through to its logical end. A while back, I built my Maverick ML7 to a point where it weighed around 21lb with pedals etc, which was light for what it was. It felt super lively accelerating out of corners etc and quicker on climbs. Definite psychological boost.

But… I would have been better off spending the same cash on a coach and personalised training plan and living with a bike that weighed two or three lb more.

You need to weigh and cost everything – all the small savings add up – and see how much it’ll cost you, then ask yourself whether proper coaching – and maybe some weight loss – won’t give you much more bang for your buck.

As a compromise, super light race wheels and tyres will make the bike feel faster, but mine got to a point where I was breaking things on any sort of normal trail ride, so it became pretty much a dedicated race bike.

I have given up worrying about weight on my XC bike. I do mainly road racing and downhill but last year I did 4 xc races. I came 3rd, 8th, 3rd and 2nd. I noticed a few things that made me change my bike to make it faster in certain circumstances.

Firstly I noticed how completely useless a lot of xc riders are at descending, even at the sharp end of a race. I probably made up most of my places overtaking on the downhills. For this reason i put bigger tyres on and a dropper. I was happy to sacrifice a bit of uphill/flat speed for the downhill speed.

I also beefed the wheels up. I used to use stans crest rims but they constantly felt like they were going to collapse. Talk about flexy. I changed them for some mavic 819’s which give the tyres a good round profile which i like for cornering.

I swapped back to flat pedals. Again its amazing how may riders cant get clipped back in after dabbing for a corner or a traffic bottleneck. Coming from road and dh where you don’t unclip much I include myself in this and the rush and heat of the moment of a race doesn’t help. I passed quite a few people on steep uphills by being able to get back on the pedals sooner.

So for me weight isn’t at the top of my list. i need a bike that’s good on the downhills and will suffer a bit of drag on the ups as a trade off.

One of the guys I ride with weighs 18st – ex rugby player- but trounces all of us fairly fit blokes on the ups. He has no interest in making his bike lighter, he just buys what’s in the shop. I try and keep my bike as light as I can afford but never seem to get anywhere near him. You can’t beat genes especially fit genes!

weeksy – do it. Sounds like you want the carbon xc bike anyway.

What i WANT is a Stanton… LOL. But i don’t think that the Stanton will give me anything that the Parkwood doesn’t give me already. Whether i wend for the Slackline and used my Hope pro4’s or whether i went for a Sherpa and used the 29er bits, i don’t think it would give me anything MORE in the context of XC racing/riding anyway.  I do think it may give me a bit of WOW that the Parkwood doesn’t give…

However the Parkwood is an absolutely EXCELLENT machine at what it does and the budget it’s at.

Interestingly i’m planning on using this weekeneds Swinley meetup to jump on both my T-130 and the Parkwood and see which one i ride quicker on over a generic XC route, i was thinking Seagull, or Stickler, whichever the flat twisty one is…. That’s the trail at Swinley that most mirrors Checkendon XC course i think, so was going to do back to back riding of it and see which of my 2 bikes i’m quicker on.

The T-130 is more flickable, better handling and dual suspension, lighter wheels. The Parkwood has the 29er wheels, is a bit slower in the turns but rolls superbly… The answer to that question may open up all sort of other thoughts i may or may not consider.

I totally get that making myself faster/fitter/lighter is the way forward, believe me, i get that. That’s why i’m Zwifting so much, hitting the diet and trying to drop from 98kg down into the 80’s bracket, which i’m not far from now. But realistically, 88-89kg is about as low as i can really expect, i’m never going to be a 70kg lightweight bloke… the time, training, diet and comittment is WAY above me to ever reach there.

Where are you most likely to pass other riders weeksy ?

I’ve never ridden an xc race but guessing that singletrack sections are likely processions and all the overtaking happens elsewhere.

If you could smash a downhill, slightly off the preferred line on your heavier bike, might you pass more riders than you could by overhauling them on a gradual hill ?

Alternatively, are the overtaking opportunities in places where you might need to burst round somebody on a flat or upward bit, where a light bike might just make a difference ?

last year I did 4 xc races. I came 3rd, 8th, 3rd and 2nd.

What cat / level / series & how many entered? As they’re impressive results

I probably made up most of my places overtaking on the downhills.

I overtake loads of people on descents, and also flat singletrack.  However I lose it all again on the climbs, so I wouldn’t personally bother with improving my bike for the descents – I manage fine.  But improving it for climbing would help.  More time is gained or lost on climbs I think than descents generally.

Over the years I’ve come to the conclusion that making yourself lighter has more effect than making your bike lighter on how fast you are

Where are you most likely to pass other riders weeksy ?

At the Southern XC courses i’d say the passing opportunities are more likely to be on the ups than the downs, or at the least, the flat bits.  Certainly at Checkendon for sure. The main passing places there are 3 field sections, which are fairly flat (the start finish is slihglty downhill, but a wide fieldy taped off route), so really the ‘infield’ section in the majority is singletrack and non-passing unless you’re using brute force.

That kind of suits me really as i’ve got a certain amount of Watts at my disposal which could in theory mean i burst the watts on them bits and then recover in the singletrack.

However, what has happend in the past is that i’m so destroyed and breathing like i’m about to expire in the singletrack, that when i get to the flat fieldy bits i’m already trying to recover 🙂

sounds like you need to get a turbo trainer – they’re pretty good, I’ve heard

<<span style=”display: inline !important; float: none; background-color: transparent; color: #222222; font-family: ‘Open Sans’; font-size: 16px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; line-height: 22.4px; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;”>Over the years I’ve come to the conclusion that making yourself lighter has more effect than making your bike lighter on how fast you are</span>>

plus 1 your W/kg is the key and less weight makes you faster in all areas and more agile

I think we can safely say i’m OK there… 🙂

This is where Zwifting has plusses and minuses as it’s hard to replicate an XC race when sitting in the garage. The closest i can think of is the shorter races i like doing because you can end up at your limit, then needing to kick on to hold the bunch etc… In the longer races it’s often a slog on Zwift and i’m not sure how real world them sort of rides are to me. But i honestly believe that if i can”t ride in the woods, then what i am doing is hopefully the best type of effort i can do for what i want next month.

Training at Swinley/etc of course is FAR better… but very rarely do i get the chance to do so.

plus 1 your W/kg is the key and less weight makes you faster in all areas and more agile

Of course, but you can buy a bike in 24 hours that’s 2kg lighter than your current bike… .Dropping weight is a LOT harder and a much slower process.

As i’ve stated, i’ve dropped almost 10kg in 2018, so it’s not like i’m not already doing my best on that side of things..

This is where Zwifting has plusses and minuses as it’s hard to replicate an XC race when sitting in the garage.

Try something like sufferfest or trainer road for some much higher intensity workouts and intervals,

Try something like sufferfest or trainer road for some much higher intensity workouts and intervals,

Last Zwift race i did was at an average of 170bpm, with my absolute max of 182…. i’m not convinced anything outisde of a pack of rabid dogs could make me work harder 🙂

Intervals, yes, i’ll give you that… But i’m not a trainer road kind of guy.

It’s more about the variety and structure than just going hard for some time, if you get the sufferfest humour then it’s good at motivating you

last year I did 4 xc races. I came 3rd, 8th, 3rd and 2nd.

What cat / level / series & how many entered? As they’re impressive results

sorry i did 5 not 4.

2 x elite. the 8th and an 11th

3 x enthusiast ( or whatever its called) 3rd 3rd and 2nd