Wrong crank length on new bike

blueturtle

Hi all, in a bit of a dilemma just purchased a De Rosa sk pininfarina size 48cm from Wiggle which arrived yesterday. Unfortunately to my surprise the crank length was 172.5mm. Unusual for this size frame in my experience as all my other bikes size 50cm that I have bought came with 170mm cranks .Indeed I e-mailed Wiggle two weeks ago to confirm crank length on a 50cm model and they confirmed that crank size was 170mm I then as it turned out wrongly assumed that the 48cm De Rosa would come with cranks 170mm-165mm certainly not 172.5mm. My problem is do I keep my purchase or send it back,Knowing that this was the last bike in this spec and all I would get would be a refund. I have perused various sites getting information on crank lengths which has made me totally confused . I would like keep the bike but am reluctant to spend a large some of money on a bike which I cant get along with.PS I know I could keep the bike and exchange the cranks but for two reasons I do not want to do that, 1, reluctant to start stripping new bike. 2,i always seem to be out of pocket doing these sort of exchanges. Thanks in anticipation for your advice. PPs I have only ridden with 170mm cranks so have no experience with any other size.

mercia_man

If you are happy with 170mm cranks, I think you will be fine with 172.5. I doubt you will notice any difference. I ride both 170 and 172.5 on my bikes with no problems. They feel the same. I used to have a mountain bike with 175 cranks and I could tell a very slight difference between that and 170 but it was certainly no big deal.

cougie

I really doubt you'll notice any difference. I can't tell.

daniel_b

I think you will be fine mate, it's such a small difference in the scheme of things.

Worst case, you remove the chainset as nearly new, sell it on here, and source one that is 170mm, but I doubt it will come to that.

Have you approached Wiggle to see if they can do anything - ie is the spec correct?

I ride 175 and 172.5 and couldn't tell the difference.

sloppyschleckonds

Is toe overlap an issue?

blueturtle

No I don't believe it will be an issue.certainly with me as I currently ride a Cervelo r3sl 51 cm and that does have toe overlap but has never been a problem.

Matthewfalle

You won't notice a jot of difference.

svetty

It's frustrating when a bike isn't exactly right - I'd be irritated too - but in the real world the difference is so marginal as to be not worth worrying about it.

noodleman

I agree with the others. You'll never notice the difference. Enjoy the bike. I absolutely love mine!

trivial_poursuivant

Ridden 165mm 172.5mm. Now all my bikes are 170mm only really out of the fact that’s the middle of the road size I stuck with - mainly due to my power meter being that length. I didn’t notice any difference in performance and 2.5mm in saddle height is barely noticeable

joey54321

I can totally tell the difference between 170 and 172.5, and especially for smaller riders/smaller bikes it would be even more important to get right.

I'd email wiggle/De Rosa and ask about it or just buy a new 170 crankset and sell the 172.5 on as new.

trivial_poursuivant

joey54321 wrote:

I can totally tell the difference between 170 and 172.5, and especially for smaller riders/smaller bikes it would be even more important to get right.

I'd email wiggle/De Rosa and ask about it or just buy a new 170 crankset and sell the 172.5 on as new.

168cm and I’ve not noticed any great difference so that’s not completely true

fenix

Just ride it and see if you can tell. I know I can't tell - and seemingly you weren't bothered if it was going to be 165 or 170 anyway ?

It's a pricey bike anyway so if you did need to sell on the cranks (unlikely) then a 2nd hand pair wouldnt break the bank ?

trivial_poursuivant

Back to original post. I’m not sure how big websites like Wiggle work but Inwould have thought a bike would arrive from the manufacturer prebuilt and wiggle only really check them over for issues and don’t build up the bikes from scratch. To that I cannot understand why De Rosa would put such long cranks on what is the smallest frame size in the range, unless Wigglechave swapped it out somewhere to fulfill an order possibly. Seems a weird thing to be standard practise on behalf of the manufacturer

Steve-XcT

Trivial poursuivant wrote:

joey54321 wrote:

I can totally tell the difference between 170 and 172.5, and especially for smaller riders/smaller bikes it would be even more important to get right.

I'd email wiggle/De Rosa and ask about it or just buy a new 170 crankset and sell the 172.5 on as new.

168cm and I’ve not noticed any great difference so that’s not completely true

I have used 175 and 170's (on MTB) and the 175's kill me...
I'm almost 50 and I'll have sore joints for a week or more on the 175's... if I ride any meaningful distance whereas on 170mm no problems at all. When I used to ride road I had 175mm (and I ain't grown since)
Although a lot of you guys are younger wrong length cranks are still putting strain on the joints.. you probably don't feel it like us older guys but it's a pretty good chance that by the time you are the old guy the damage may be done.

If I could roll back time I'd stick 170's on my road bikes... (there are a few crashes I'd avoid as well whilst we are at it)
I don't know if it would make a difference for sure but I suspect it would...

noodleman

Trivial poursuivant wrote:

Back to original post. I’m not sure how big websites like Wiggle work but Inwould have thought a bike would arrive from the manufacturer prebuilt and wiggle only really check them over for issues and don’t build up the bikes from scratch. To that I cannot understand why De Rosa would put such long cranks on what is the smallest frame size in the range, unless Wigglechave swapped it out somewhere to fulfill an order possibly. Seems a weird thing to be standard practise on behalf of the manufacturer

I could be wrong but having owned two de rosa bikes I'm pretty sure they are built up by either a company called i-ride or by the final seller. Wiggles de rosa's are definitely supplied by i-ride.

lesfirth

I bought a bike a few months ago from Chain Reaction. Their online spec. said 105 GS rear mech and 28mm tyres. Bike arrived with 105 short cage and 25mm tyres. I contacted CRC and after receiving some photos they sent me some 28mm tyres and a GS rear mech without hesitation. They did not ask me to return the wrong parts. Problem sorted and one satisfied customer.

dj58

If the spec. says they should be 170mm and that is what you want, politely but firmly ask them to send you a set of the required length and offer to return the 172.5mm using their free returns service.

Matthewfalle

DJ58 wrote:

If the spec. says they should be 170mm and that is what you want, politely but firmly ask them to send you a set of the required length and offer to return the 172.5mm using their free returns service.

There’s probably a caveat saying that parts liable to change yada yada yada

Matthewfalle

Trivial poursuivant wrote:

joey54321 wrote:

I can totally tell the difference between 170 and 172.5, and especially for smaller riders/smaller bikes it would be even more important to get right.

I'd email wiggle/De Rosa and ask about it or just buy a new 170 crankset and sell the 172.5 on as new.

168cm and I’ve not noticed any great difference so that’s not completely true

6’2 here and used 170, 172 and 175. Not a jot in difference.

blueturtle

Hi all, thanks for all the replies re. crank length. One point that is giving me concern is the disparity between crank length on the De Rosa and what Canyon suggest is ideal for my size.I was thinking of purchasing a Canyon Aeroad. Size xxs is what they suggested given my measurements (165cm height and 76 mm inside leg length. their bike came with 165mm cranks. If you read all the bumff from all the internet experts they suggest that my size would probably require 165mm cranks. However most bike manufacturers supply 170mm for my size frame.As I have always ridden with 170mm cranks I was happy to stay with that size,but moving up another 2.5mm might just be pushing the envelope a little to far.Anyway thanks again for all your replies.It looks that I will just have to suck it and see.Got 12 months with the Wiggle return policy!!

cq20

Similar height (166cm), shorter legs (74.5cm) and although I’m OK ish with 170 cranks, I much prefer 165s. I can't get on with cranks longer than 170 (I’ve tried) but the the fact of the matter is that for most bikes I know I have to replace the standard fit cranks which will be 170s anyway. Canyon are the exception here. It isn’t that expensive to source Shimano 165 cranks and you can always sell the 172.5s or keep them to swap back when you change to a new bike.

StillGoing

joey54321 wrote:

I can totally tell the difference between 170 and 172.5, and especially for smaller riders/smaller bikes it would be even more important to get right.

I'd email wiggle/De Rosa and ask about it or just buy a new 170 crankset and sell the 172.5 on as new.

Same here. But of course, because there are those that can't tell any difference, they wrongly assume that nobody can. :roll: If you want to ride with a high cadence, the shorter crank length makes it easier (less distance overall turning circle) and the difference between 172.5 and 170mm crankset is not 2.5mm, it is 5mm. A 172.5mm crank set has a diameter of 39cm giving a circumference of 122.5cm. A 170mm crankset has a diameter of 34cm and a circumference of 106.8cm. In terms of time/distance; for a distance of 106.8 miles and 122.5 miles both travelled at 100mph, the time difference is 1:4.05 and 1:13.30 respectively. It therefore would take longer to complete a full rotation of the pedals for the different crank lengths at the same cadence.

The major benefit is in the increased clearance at the top of the pedal stroke making it less restricted getting on to the greatest power in the down stroke.

If you're a rider that is happy and can't tell the difference between crank lengths, good for you. But there are those of us that can and do benefit from shorter cranks.

trekvet

I would accept what *I* wanted, and not what the shop sent..What does De Rosa website say?

wavefront

philthy3 wrote:

and the difference between 172.5 and 170mm crankset is not 2.5mm, it is 5mm. A 172.5mm crank set has a diameter of 39cm giving a circumference of 122.5cm. A 170mm crankset has a diameter of 34cm and a circumference of 106.8cm. In terms of time/distance; for a distance of 106.8 miles and 122.5 miles both travelled at 100mph, the time difference is 1:4.05 and 1:13.30 respectively. It therefore would take longer to complete a full rotation of the pedals for the different crank lengths at the same cadence.

We might have to send you back to school! Have a re-read, both your maths and physics need correcting

StillGoing

wavefront wrote:

philthy3 wrote:

and the difference between 172.5 and 170mm crankset is not 2.5mm, it is 5mm. A 172.5mm crank set has a diameter of 39cm giving a circumference of 122.5cm. A 170mm crankset has a diameter of 34cm and a circumference of 106.8cm. In terms of time/distance; for a distance of 106.8 miles and 122.5 miles both travelled at 100mph, the time difference is 1:4.05 and 1:13.30 respectively. It therefore would take longer to complete a full rotation of the pedals for the different crank lengths at the same cadence.

We might have to send you back to school! Have a re-read, both your maths and physics need correcting

OK, hasty typing whilst rushing out of the door. :oops: The gyst is the same though in that the radius for the pedal circle is 170mm. The diameter is therefore 2 x 170mm = 340mm or 34cm. The circumference will be 106.8cm.
For a radius of 172.5mm, the diameter will be 345mm or 34.5cm a difference of 5mm. The circumference will therefore be 108.3cm.

For a distance of 50km, the 170mm cranks would need to go through 4681 revolutions or 499930.8cm. The 172.5mm cranks would go through 4613 revolutions or 499587.9cm. So, less revolutions for the longer cranks, because of the greater turning circle. But, the advantage is for the shorter rider to have more clearance at the top of the pedal stroke.

http://bikedynamics.co.uk/FitGuidecranks.htm

trivial_poursuivant

philthy3 wrote:

wavefront wrote:

philthy3 wrote:

and the difference between 172.5 and 170mm crankset is not 2.5mm, it is 5mm. A 172.5mm crank set has a diameter of 39cm giving a circumference of 122.5cm. A 170mm crankset has a diameter of 34cm and a circumference of 106.8cm. In terms of time/distance; for a distance of 106.8 miles and 122.5 miles both travelled at 100mph, the time difference is 1:4.05 and 1:13.30 respectively. It therefore would take longer to complete a full rotation of the pedals for the different crank lengths at the same cadence.

We might have to send you back to school! Have a re-read, both your maths and physics need correcting

OK, hasty typing whilst rushing out of the door. :oops: The gyst is the same though in that the radius for the pedal circle is 170mm. The diameter is therefore 2 x 170mm = 340mm or 34cm. The circumference will be 106.8cm.
For a radius of 172.5mm, the diameter will be 345mm or 34.5cm a difference of 5mm. The circumference will therefore be 108.3cm.

For a distance of 50km, the 170mm cranks would need to go through 4681 revolutions or 499930.8cm. The 172.5mm cranks would go through 4613 revolutions or 499587.9cm. So, less revolutions for the longer cranks, because of the greater turning circle. But, the advantage is for the shorter rider to have more clearance at the top of the pedal stroke.

http://bikedynamics.co.uk/FitGuidecranks.htm

Completely pointless statements. Fact of the matter is the bike didn’t come with the correct part as one would expect. If the owner can tell the difference or not or if the amount of toe overlap blah blah etc, not important! If I order a bike expecting a certain component and it came with different I’d be concerned and want it rectifying.

wavefront

philthy3 wrote:

For a distance of 50km, the 170mm cranks would need to go through 4681 revolutions or 499930.8cm. The 172.5mm cranks would go through 4613 revolutions or 499587.9cm. So, less revolutions for the longer cranks, because of the greater turning circle.

Ok, maths sorted, unfortunately logic still a little flawed :?

If you're saying riding 50km on a bike with a smaller crank length will require less pedal revolutions then perhaps mount your bike on your turbo, and closely try and observe this for real.

If you're saying your feet may physically move slightly less in a rotational distance with a smaller crank length for a given distance travelled by the bike then yes, but how does that matter?

The guy who does bike fits at Sigma Sport talks a lot of sense. Forward to 3.35

https://m.youtube.com/watch?v=pKccqlqoJGQ

StillGoing

wavefront wrote:

philthy3 wrote:

For a distance of 50km, the 170mm cranks would need to go through 4681 revolutions or 499930.8cm. The 172.5mm cranks would go through 4613 revolutions or 499587.9cm. So, less revolutions for the longer cranks, because of the greater turning circle.

Ok, maths sorted, unfortunately logic still a little flawed :?

If you're saying riding 50km on a bike with a smaller crank length will require less pedal revolutions then perhaps mount your bike on your turbo, and closely try and observe this for real.

If you're saying your feet may physically move slightly less in a rotational distance with a smaller crank length for a given distance travelled by the bike then yes, but how does that matter?

The guy who does bike fits at Sigma Sport talks a lot of sense. Forward to 3.35

https://m.youtube.com/watch?v=pKccqlqoJGQ

I'm saying shorter cranks will require more revolutions if you read it.

I fully support the view that shorter cranks matter for shorter riders or those who prefer a high cadence. I rode with the standard 172.5mm cranks for a long time, suffering with knee pain and hip problems. Moving to 165mm cranks has saved those issues. As I posted earlier, there will be those who can't tell the difference and pooh-pooh the very notion of it being any help. But there are those of us can tell the difference and do find it a help.

veronese68

The transfer from one revolution of the cranks to how far the wheel moves is nothing to do with crank length but everything to do with gearing. If you put a bike in a stand and push the crank halfway along it's length the wheel will turn the same amount as if you push on the pedal. A longer crank is a longer lever so there is less force required on the end of it, but the pedal has to travel a longer distance as the circumference of the circle is larger. Shorter cranks are easier to spin, but being a shorter lever need more force applying.
With respect to the difference in lengths of cranks. Some people are more sensitive to changes than others, so what one person notices another may not. I'd try to get them replaced if you are not happy.

daniel_b

Crank length has nothing to do with the amount of revolutions required.

Doesn't matter if they were 100mm or 200mm, they still need to revolve the same number of times.