Seat post length in Reynolds 753 frame

Discuss light weight issues concerning road bikes & parts.
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Penthousepete
Posts: 33
Joined: Sun Apr 21, 2013 2:56 pm
Location: Bournemouth, UK

by Penthousepete

Hi
I'm building a retro steel TT bike and for the silver bling look was going to use a Thompson post (undecided on Elite or MP) and given they come in 250 or 330mm lengths I'm unsure which length to go for. I can't find what the minimum insertion is on their site and I'd probably say I need about 90mm in the frame if I use a 250mm post. I've been advised it's a balance also of the frame material too. Frame is Reynolds 753 and I'd prefer the shorter length, but don't want to risk issues...

Thoughts and any help very welcome!
Losing weight is an education
Hong Fu Bikes FM0069 Superlight 2014 6.35kg (SRAM Red, Tune TSR30)
Cannondale Flash F1 '10
Felt Brougham '10

ghisallo2003
Posts: 598
Joined: Mon Jan 02, 2006 7:10 pm

by ghisallo2003

Insertion lengths are listed on the website under the 'specs'.

Don't forget you can also buy long and then cut off unnecessary length.

latman
Posts: 123
Joined: Thu Aug 20, 2009 12:44 pm

by latman

As a very minimum I think the seatpost needs to go past the top tube lug

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Stolichnaya
Posts: 2622
Joined: Wed Oct 06, 2004 6:55 pm
Location: Vienna, AUT

by Stolichnaya

As you mention this is a retro steel TT frame, then it might have fastback seat stays, so you should go considerably beyond the seat tube lug.
With my older steel frame I have a minimum insertion of 8 to 10 cm from the top of the seat tube lug. But that might be overkill if you are a lighter rider.

RussellS
Posts: 722
Joined: Wed Feb 03, 2010 1:31 am

by RussellS

I have a Waterford 2200 frame. Lugged, Reynolds 753, silver brazed. Fastback style seatstays. The seatstays come close to each other at the back of the lug below the bolt. American Classic aluminum seatpost. Old style, original post. 13cm of shaft sticking out of the lug. Assume the post is 25cm total. So about 12cm of post in the seattube. Not sure where the minimum insertion line on the post is. Guessing the minimum line is about 8-10cm from the bottom. So your 9cm inserted in the seattube is right near the minimum insertion line. I would say you will be OK with the 25cm post from Thompson. You'll be right near the minimum insertion line. Few millimeters either way. Doubt it will matter either way. I do not think the Reynolds 753 tubing will care. Mine has held up fine for 17 years.

ghisallo2003
Posts: 598
Joined: Mon Jan 02, 2006 7:10 pm

by ghisallo2003

In fact, don't worry about it: it will cold weld in no time.

Penthousepete
Posts: 33
Joined: Sun Apr 21, 2013 2:56 pm
Location: Bournemouth, UK

by Penthousepete

Thanks for the replies, I've attached a pic of the lug at the top of the tube. Couldn't find the spec on the site, but think at 90cm should be ok. Im 185lb or 84kg and have been told both the Elite and the Masterpiece are pretty much bomb proof, just need the tubes to hold out. Guessing they will as its not carbon...
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Losing weight is an education
Hong Fu Bikes FM0069 Superlight 2014 6.35kg (SRAM Red, Tune TSR30)
Cannondale Flash F1 '10
Felt Brougham '10

mattyNor
Posts: 276
Joined: Wed Mar 19, 2014 3:18 pm

by mattyNor

Just get the long one and cut it down as needed.

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