# 43mm vs 45mm Rake



## MTBMaven (Dec 17, 2005)

Assuming everything else is equal, how noticeable is the difference between 43mm and 45mm rake? 

I do long rides (centuries and doubles) and climb a lot of mountains training. Average training ride is 17-25 miles with 2,000-3,000 feet of gain.


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## PJ352 (Dec 5, 2007)

MTBMaven said:


> Assuming everything else is equal, how noticeable is the difference between 43mm and 45mm rake?
> 
> I do long rides (centuries and doubles) and climb a lot of mountains training. Average training ride is 17-25 miles with 2,000-3,000 feet of gain.


Assuming all else is equal, changing rake between 43mm and 45mm will change resulting trail by about 2mm. From 43mm to 45mm -2mm, 45mm to 43mm +2mm. I doubt you'd notice that difference. You already may know this, but changing trail affects steering. Less trail, quicker steering - more trail, slower steering.


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## AlexCad5 (Jan 2, 2005)

I changed from a 45mm to a 43mm on my first recent road bike, a Cannondale Caad5 (I wanted a full carbon steerer.) It did two unexpected things. First, the bike no longer had a twitchy feel which Cannondales have been occasionally accused. It still was quick steering but it lost it's nervousness. And oddly enough, that 2 mm made me aware of toe overlap, which with over one year on that bike, I had never noticed before. YMMV


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## PJ352 (Dec 5, 2007)

AlexCad5 said:


> I changed from a 45mm to a 43mm on my first recent road bike, a Cannondale Caad5 (I wanted a full carbon steerer.) It did two unexpected things. First, the bike no longer had a twitchy feel which Cannondales have been occasionally accused. It still was quick steering but it lost it's nervousness. And oddly enough, that 2 mm made me aware of toe overlap, which with over one year on that bike, I had never noticed before. YMMV


Going from a 47mm to a 43mm on my Serotta I expected a more noticeable change than what I experienced, but the bike has a more 'relaxed' geo than say, the HSG line which may be a contributing factor. I ride a 51cm, so toe overlap has been a part of the picture for 22 years.


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## Pablo (Jul 7, 2004)

You should probably use the fork rake your frame was designed for.


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## kiwisimon (Oct 30, 2002)

If it's for your new custom trust the builder to know what is best. Is it for an existing bike?


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## flanman (Jul 7, 2006)

I had a very twitchy bike. Changed the rake from 43 mm to 40 mm and it certainly had an effect. You don't really feel it in normal riding but it made the difference between not being able to ride no hands and being just about able to. I feel that reduced twitchiness should have some effect on reducing fatigue over long rides - your body has to make fewer corrections - but this is a difficult thing to prove.

That said, bikes that are stable at low speed may not handle well at higher speeds and vice-versa.

If it's a well-designed bike, changing rake by 2 mm probably won't have a noticeable effect, you may notice a slight change in response riding no-hands or when using aerobars, but if the bike is on the cusp of twitchiness, that change may have a larger effect to lessen or magnify twitchiness to a noticeable degree.

There's some discussion of stability criteria in the book Bicycling Science, but I can't recall the form of the equations.


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## CurbDestroyer (Mar 6, 2008)

How much does a fork flex? I mean you can switch from on rake to another, but you also have to consider how ridged it is.


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## Gunther (Jul 28, 2004)

Not a whole lot, *all other factors being equal*. I just went through this ordeal and ended up moving from a 43mm to a 44mm rake. The new fork also had the correct fork-to-crown dimension for my bike which happened to be about 5mm MORE than the old fork. With the old fork, handling was twitchy and the bike was prone to shimmy at speeds >35. With the new fork, the bike handles like a dream. I've only checked up to 45 so far, but it was hands off stable at that point.

GtB


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## MTBMaven (Dec 17, 2005)

Um lot of questions to try and answer. I am having a steel De Salvo built right now, well I'm on the wait list. I will be porting most parts from current bike to the De Salvo. This includes my Reynolds Ouzo Pro carbon fork, which has 43mm rake. 

Right now the fork is on a Lemond Zürich, which is on the twitchy side. I must say I am a bit of a newb when it comes to road bikes. I have had the Lemond for about 16 months. This is my first road bike so I don't have a huge history to rely on. I will be discussing things with Mike when we get closer to the build time. 

I built up my dad's '89 Specialized Sirrus lugged steel frame this past summer. I find this bike far more stable in that I can comfortably ride without hands. I will not do this on my Lemond as I don't feel comfortable. Not sure what all this means (remember the lack of experience here). I have read enough to know that rake may have a play here; hence the questions about fork rake. Thanks for all the feed back thus far.


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## DaveT (Feb 12, 2004)

All things equal, the 43 rake fork will slight slow the handling of the bike vs the 45 rake fork, that is less 'twitchy'.

If you're having Mike DeSlavo build you a frame, he's going to specify what rake fork he has designed the frame for. If you are going to put a 43 rake fork on your DeSlavo, he needs to know that.


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## Sweet Milk (Oct 13, 2004)

Swapping forks can have very significant handling effects. These are due to changes in rake, but also crown to race distance and rigidity. I once thought I had cured the handling problems on a bike by going to a 40 mm rake fork. When that fork broke in an accident I replaced it with another 40 mm rake fork, only to find out that the difference was really due to the differing amount of flex in the fork and not the rake.


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## AlexCad5 (Jan 2, 2005)

PJ352 said:


> Going from a 47mm to a 43mm on my Serotta I expected a more noticeable change than what I experienced, but the bike has a more 'relaxed' geo than say, the HSG line which may be a contributing factor. I ride a 51cm, so toe overlap has been a part of the picture for 22 years.


 The 43 would make it more stable, so you would probably only notice it in tight turning situations, or steep twisty descents. I assume the 51cm bike had a 47mm rake in order to reduce toe overlap, and to offset the slack head tube (also to reduce toe overlap.)
I agree, toe overlap is something you work around.


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## AlexCad5 (Jan 2, 2005)

Gunther said:


> Not a whole lot, *all other factors being equal*. I just went through this ordeal and ended up moving from a 43mm to a 44mm rake. The new fork also had the correct fork-to-crown dimension for my bike which happened to be about 5mm MORE than the old fork. With the old fork, handling was twitchy and the bike was prone to shimmy at speeds >35. With the new fork, the bike handles like a dream. I've only checked up to 45 so far, but it was hands off stable at that point.
> 
> GtB


 It doesn't make sense that your bike was more stable a longer rake. You might have also changed another factor as well, and are not accounting for it.
Hands free stable at 45mph? Braver than I.


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## toyota (Sep 4, 2006)

AlexCad5 said:


> I changed from a 45mm to a 43mm on my first recent road bike, a Cannondale Caad5 (I wanted a full carbon steerer.) It did two unexpected things. First, the bike no longer had a twitchy feel which Cannondales have been occasionally accused. It still was quick steering but it lost it's nervousness. And oddly enough, that 2 mm made me aware of toe overlap, which with over one year on that bike, I had never noticed before. YMMV


 not sure if Im reading your post correctly but if you think your stock Caad5 came with a 45 rake then you are mistaken. caad5 has 43 across the whole size range.


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## artiefox1956 (Oct 14, 2021)

AlexCad5 said:


> Cannondale Caad5


What is the head angle on your cannondale Caad5?


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## artiefox1956 (Oct 14, 2021)

toyota said:


> not sure if Im reading your post correctly but if you think your stock Caad5 came with a 45 rake then you are mistaken. caad5 has 43 across the whole size range.


Will this make a bike that is stable at slow and fast speeds? 73.5 parallel frame, 40.5 chain stays, 58 top tube. 43 mm rake. 72 mm BB drop? Threadless 12 cm stem.


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## cxwrench (Nov 9, 2004)

artiefox1956 said:


> Will this make a bike that is stable at slow and fast speeds? 73.5 parallel frame, 40.5 chain stays, 58 top tube. 43 mm rake. 72 mm BB drop? Threadless 12 cm stem.


The post you're replying to was made in late April 2008...don't be surprised if you don't get an answer to your question form the guy you quoted. Can't really answer your question accurately but I'd say more stable than not, and more stable at higher speeds.


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