Geometry advice needed - matching new to older bike

Beansontoast

Hi Radars,

I have an interesting question on the subject of bike geometry, which is something I have never paid much attention to.
Maybe I should have!

After recently upgrading to a Giant Trance2 2015, from a Specialised Pitch Pro 2009 I have been struggling for months on the big long climbs. Fitness is the same, and as far as "bling" goes the Trance 2 wins hands down (27.5, 1x10, tubeless).

Today I finally got the tape measure out and noticed a couple of things compared to the Pitch -

1 The tip of the front seat on the Trance is two or three inches further back in relation to the bottom bracket, than it is on the Pitch. So I'm sat further back, which has obviously been impacting my climbing (massively)

2 The tip of the seat to the top tube is a couple of centimetres closer. So a smaller cockpit feel. If I simply move the seat forward to help with the climb, it can start to feel a bit cramped.

The question I have, is apart from going out and measuring the different Geometry on different bikes (which is unrealistic for a lot us, especially in the second-hand market), are there any resources out there which can help with this?

I can see now just how critical the geometry is, but never paid too much attention to it.
With hindsight, what I would have loved to have done, was move to a new bike, but one with similar Geometry to the last one. The Pitch was an awesome bike, and although the Trance2 is also great, it looks like its not set up with the climb in mind.

So - any ideas or suggestions for those of us who may want to research, or match-up the geometry of their old bike a newer one.

Advice appreciated.

The Rookie

Presumably you mean the tip of the saddle is closer to the head tube, closer to the top tube wouldn't be relevant.

When looking at Geo charts its not too hard, you look at the seat tube angle (and allow for any seatpost offset) for your dimension 1 and at the effective top tube length (again allowing for seatpost offset) for dimension2. For 2 also take note of the stem length and bar width as that affects how long the cockpit is on a subjective basis.

Seat tube angle on a Trance (found a 2014 and 2016 and they are the same) is 73.5 a Pitch (2010) is 74 but the kinked tube should make it relatively more upright with the saddle further forward compared to the BB.
Effective Top tube is 585mm (Medium) the Pitch is 586mm (Medium).

So I'm not sure how you've got to your numbers you've measured.

robertpb

I don't see any mention of stem length or bar width here as they would also make a difference.

Also your measuring seems a bit vague, also if your saddle is too far back and moving it forward makes the bike cramped it sounds like either the stem is shorter on the Trance or it's a smaller frame.

Beansontoast

Ok, Thanks for the replies.

Just to clarify, yes I meant seat-tip to head post - bit of a schoolboy error on that one.

Bear with me while I get a couple of pictures sorted and I will overlay the measurements, technology permitting.

In the meantime, to summarise and provide clarity -

Seat-tip to headpost - more room on the Pitch (about 2.5 cm's)
Seat-tip to alignment-with-bottom-bracket - much closer on the pitch (so much better on the climb).

And both are medium, although I realise there are significant differences in manufacturers here.

robertpb

Measure from the seat tube to the head tube horizontally, that may be where the difference is, one is just a longer frame than the other.

Uber_Pod

Google is your friend.

These might help (scroll to the bottom)
https://www.specialized.com/us/en/bike- ... hpro/22265
https://www.giant-bicycles.com/gb/trance-27dot5-2-2015

Beansontoast

Ok, got some pics.

With everything set up identically - seat height and saddle centred, there is very little difference in seat-tube to headtube.

However, there was a 60 mil difference in seat-tip to bottom bracket, which is related to a slacker seatpost angle on the Giant (basically, it leans further back).

When you look at the pics, its pretty dramatic and that will obviously have an impact on climbing as your weight on the saddle is 60 mils further back than on the pitch. If you then move the seat further forward, you end up taking room of the cockpit (bar-ends hit your knees tc).

I think the bottom line, is the variations in geometry are significant and some of the important ones are probably not spelt out, or that obvious in geometry specs. I think next time I'll have to do more research, maybe even get the tape measure out.

In particular the seat-tip to bottom bracket relationship (well I think that's the bottom bracket\ "crank centre") makes a difference to the climb.

Anyhow, here's some pics, maybe explains things with a bit more clarity -

The Trance - clearly showing 60mil behind the centre point of the crank (is the the BB?) -



The Pitch - only a couple of mil behind -



The Giant - 60mil close up



OK - I hope that's clear, and maybe useful for those who are upgrading, who knows?

If I'm wrong on the seat being further back behind the point of the BB, then happy to discuss, but it seems to be making a big diference to me on the big climbs.

Beansontoast

OK - Got a bit more useful info on this one.

I think what is important in regards to Geometry are several key measurements which don't seem to be easily available on manufactures websites, but do show up on some of the review sites.

The best one I've seen so far is enduro-mtb.com. Although they seem a bit obssessed with the top-end, they summarise all their reviews with the following geometry measurements -

Top Tube Horizontal
Seat Tube Angle
Chainstays
Head Tube Angle
Wheelbase
REACH
stack

Unfortunately I can't find an example of the Pitch Pro, but this is a useful site and useful stats at a glance.

Have a look at this -



There is an example for the Stumpjumper review here -

http://enduro-mtb.com/en/specialized-st ... 0b-review/

The Rookie

The key dimensions (though harder to get) are reach (between vertical lines through BB and headtube at its top) and stack (which is between horizontal lines through the same), then as long as you can put the saddle in the right place it will all be the same.

The seat tube angle is very similar between the two but the 'bent' seatpost on the Pitch moves the starting point ahead of the BB so it's effectively steeper.

If you swap in a longer saddle (have a look at the on-one bignose for example http://www.planetx.co.uk/i/q/SAOOBNES/o ... evo-saddle) then practice moving to the nose for climbs you should be sorted. Its not like the Trance is known as a bad climber, I think you just have to get dialled into it.

Beansontoast

[quote=
The seat tube angle is very similar between the two but the 'bent' seatpost on the Pitch moves the starting point ahead of the BB so it's effectively steeper.

If you swap in a longer saddle (have a look at the on-one bignose for example http://www.planetx.co.uk/i/q/SAOOBNES/o ... evo-saddle) then practice moving to the nose for climbs you should be sorted. Its not like the Trance is known as a bad climber, I think you just have to get dialled into it.[/quote]

Thanks again Rookie.

I did notice that the seat tube angle on the pitch was much more upright. I tried an "angle overlay" piece of software which looks like the angle on the pitch was only around 69 - 70 degrees, but I couldn't manage to save the image.

If that's the case, then that would explain why the seat-tip is much so much further back, coz basically the sharper angle on the giant pushes it further away from the central point (BB).

I'll have a look at that seat.

The Rookie

According to Geo charts I found the Pitch has a seattube angle of 74, flatter than the Giants 73.5?

I can't see your photo's though the Co. firewall for reference though.

Try moving forward on your current saddle first, the BN was just one longer saddle I was aware of, I'm sure there are others.

Beansontoast

The Rookie wrote:

According to Geo charts I found the Pitch has a seattube angle of 74, flatter than the Giants 73.5?

I can't see your photo's though the Co. firewall for reference though.

Try moving forward on your current saddle first, the BN was just one longer saddle I was aware of, I'm sure there are others.

Ok - the plot thickens.
Finally found an on-screen projector that works and was easy to use -

https://sourceforge.net/projects/osprot ... p_redirect

You are correct on the Pitch seat tube angle being 74 from what I can see (there will be minor inaccuracies but pretty close overall).

However, the giant is only showing as a 69. So five degrees slacker. IF correct, then that is pushing the seat further back.

There's two more pics here (soz you can't see them just yet).

Showing the angle of the Pitch -



Showing the angle of the Giant -

The Rookie

Every Trance I can find states 73.5, where did you find a 69?
2017 https://www.giant-bicycles.com/gb/trance-1
Noting that the head tube angle is 69, but surely you've not been that silly?

Beansontoast

The Rookie wrote:

Noting that the head tube angle is 69, but surely you've not been that silly?

Well .... it has been known!

No, seriously - when I photographed the Trance and ran the On-screen protractor over it, the angles show as around 69. Maybe 70 as there is bound to be room for error. Have a look at the pics when you are firewall-free and see what you think.

Your'e right about the 73.5 being present on the Trance2's. Even my exact model has it at that -

https://www.giant-bicycles.com/us/trance-27dot5-2-2015


It's an interesting one for sure. The Trance climbs OK, but I definitely notice it for the worse on the bigger climbs. Maybe it just that the Pitch was a phenomenal climber and I never realised just how good it was. Plenty of changes from a 2009 26er to 2015 27.5 too. Maybe there are other factors in there that I'm not picking up on.


Probably goes to show the difficulties with buying a new bike if you don't fully understand, or haven't paid enough attention to the geometry and what it all means.

Thanks for that chat so far.