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Schwinn 4 Banger to Straight 6..?
http://www.retrobike.co.uk/forum/viewtopic.php?f=41&t=213837

Author:  Barneyballbags [ Tue Jul 31, 2012 10:08 am ]
Post subject:  Schwinn 4 Banger to Straight 6..?

I've seen 4 Bangers which have been converted to Straight 6's by using nothing more than a longer stroke rear shock.

The rear shock on a 4 banger is a Rockshox Deluxe (Coil), with a trunnion top mount and a 1.5" stroke (I think). I'm guessing that, so long as you could find a 2" stroke shock with threads for a trunnion mount at the top, then it would fit provided the threads are in the right place for the trunnion to mount to the frame?

The shock which is currently fitted. Hopefully this should clarify what I'm on about:

Image

I've had a quick look on some of the other forums to see what people say. I just wondered whether there was anyone on here who owned a 4 Banger and knew what to do?

Thanks :)

Author:  Barneyballbags [ Tue Jul 31, 2012 10:27 am ]
Post subject: 

PS.

I realise that adding a longer stroke shock will jack the back end up a little bit. However the 4 Banger has a relatively low back end anyway, plus I'd be adding some 130mm travel forks up front at the same time, to even things out.

Author:  Baulz [ Tue Jul 31, 2012 2:25 pm ]
Post subject: 

You don't need a specific shock for the trunion mount. I just found a regular 2" stroke shock on ebay, although it barely had enough threads on it to work. With the longer fork it should be ok.

I have always wondered what other brands of shock would work with the stock trunion, it would be nice to have more modern options.

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Author:  Barneyballbags [ Tue Jul 31, 2012 3:15 pm ]
Post subject: 

Thanks for the info - I did see your Homegrown when I was having a search of the forum before - very 8)

I'd assume that any Fox coil shock would work then, provided the dimensions are correct..?

Author:  Baulz [ Tue Jul 31, 2012 4:00 pm ]
Post subject: 

Barneyballbags wrote:
Thanks for the info - I did see your Homegrown when I was having a search of the forum before - very 8)

I'd assume that any Fox coil shock would work then, provided the dimensions are correct..?


I think Fox uses a different thread pitch on the shock body so it will not work with the 4 Banger trunion.

Author:  Barneyballbags [ Tue Jul 31, 2012 7:09 pm ]
Post subject: 

Good to know, thanks :)

Are there any air shocks which can be used with a trunnion mount.. Or is that a stupid question.

I think a decent air shock would completely transform it :)

Author:  Baulz [ Tue Jul 31, 2012 8:42 pm ]
Post subject: 

Someone on the mtbr Schwinn forum made an adaptor for a Fox, but it was pretty weird looking. Risse may have made shocks that work, they did trunion mounts for GT LTS frames.

There is of course the Sid rear shocks that came with some 4 bangers, mine came with one but quickly changed it for a coil.

Author:  greenstiles [ Wed Aug 01, 2012 1:41 pm ]
Post subject: 

I had a 4 banger...........but only riased and lowered the shock to it's maximums/minimum hights...........i was was trying to get a less laid back headangle as steeing was too laidback for me..........but when i raised everthing forward the bb hight was too high and the effective t/tube shrank.......and then i wished i'd bought the next size up :cry:

Have you run the shock up and down the trunion to get a different hight yet ?

ps watch for cadle outer rub on the carbon

Author:  Barneyballbags [ Wed Aug 01, 2012 2:19 pm ]
Post subject: 

greenstiles wrote:
I had a 4 banger...........but only riased and lowered the shock to it's maximums/minimum hights...........i was was trying to get a less laid back headangle as steeing was too laidback for me..........but when i raised everthing forward the bb hight was too high and the effective t/tube shrank.......and then i wished i'd bought the next size up :cry:

Have you run the shock up and down the trunion to get a different hight yet ?

ps watch for cadle outer rub on the carbon


I haven't got the bike yet. I'm just waiting for another bike of mine to sell on eBay before I buy it. I was just asking the question so I knew what was what when I got it.

Author:  greenstiles [ Wed Aug 01, 2012 2:43 pm ]
Post subject: 

May i ask what size it is and how tall you are ?

Author:  Barneyballbags [ Wed Aug 01, 2012 2:54 pm ]
Post subject: 

greenstiles wrote:
May i ask what size it is and how tall you are ?


'Tis a 17.5" (c-t I believe) and I'm about 5'9".

Author:  greenstiles [ Wed Aug 01, 2012 4:21 pm ]
Post subject: 

If that's classed as a medium i think mine was 17.5 but i'm taller so should be spot on for you.....great bike, very light, feels like more than 4 inches on the trail..........i tried altering the back end height with the trunion, worth doing 1st before you buy another shock, yes Risse did some that would have fitted i think...as for sticking a longer fork on, to be honest as the head angle is laid back a lot all ready 100mm fork is best depending on the overall fork length of course....some 100mm are longer /shorter overall than others..........i had a Psylo on there and dialed it down to about 110mm with a good sag.

Author:  greenstiles [ Wed Aug 01, 2012 4:28 pm ]
Post subject: 

Stock spring was way too soft and bobbed all over the show...got a 50lb stronger spring for it and it all came together........meaning i could climb and all the travel wasn't used up just sitting the thing :D

Author:  Barneyballbags [ Mon Aug 06, 2012 3:46 pm ]
Post subject: 

Bike is bought and paid for and will be with me by the end of the week with a bit of luck and a following wind ;)

I've been giving it some thought and I think I'll just swap out the rear spring for a stiffer one (if I need to!), rather than fitting a longer shock. Luckily for me in this instance I'm pretty skinny for my height, so the stock spring should be towards the stiff side for me anyway, fingers crossed :)

Author:  greenstiles [ Mon Aug 06, 2012 7:25 pm ]
Post subject: 

good man, when i used to ride mine it used to be with guys with more travel.......i used to expect to bottom out onmany rides but didn't and kept up with them :D

You will need a mate to measure how much push rod has been used just sitting on the bike at 1st..but you'll know when yousiton it and ride it 1st time if it needs a stronger spring............also having the correct string stiffness (you can pre load them a bit too, but mine was still too soft) you will then be able to use the rebound range more effectively.

Here a link to info on shock lengths that seems to make sence if you change your mind at some point.good luck.....just don't stick too long a fork up front.
http://forums.mtbr.com/gt/schwinn-4-ban ... 93415.html

Author:  Barneyballbags [ Mon Aug 06, 2012 7:37 pm ]
Post subject: 

greenstiles wrote:
good man, when i used to ride mine it used to be with guys with more travel.......i used to expect to bottom out onmany rides but didn't and kept up with them :D

You will need a mate to measure how much push rod has been used just sitting on the bike at 1st..but you'll know when yousiton it and ride it 1st time if it needs a stronger spring............also having the correct string stiffness (you can pre load them a bit too, but mine was still too soft) you will then be able to use the rebound range more effectively.

Here a link to info on shock lengths that seems to make sence if you change your mind at some point.good luck.....just don't stick too long a fork up front.
http://forums.mtbr.com/gt/schwinn-4-ban ... 93415.html


Thanks mate :)

As I said before, I want the back end to be quite stiff (personal preference), so I'll only be running it with about 20% sag (if that) instead of the normal 25%. Forks are Rockshox Duke SL with 100m travel and a fairly low A-C length.

Author:  greenstiles [ Mon Aug 06, 2012 10:23 pm ]
Post subject: 

sounds great......you'll have fun, they really motor along :D

Author:  Barneyballbags [ Tue Aug 07, 2012 7:20 am ]
Post subject: 

Looking at the rear shock again:

Image

It looks like I could quite easily fit a longer spring, which would mean that the trunnion is higher up on the rear shock, and in turn raising the rear end slightly and tightening up the head angle.

The spring that's fitted looks pretty short, so I'm not sure how much adjustment I'd have on the trunnion 'as is'..

I was thinking of fitting a spring for a 1.75 or 2 inch stroke shock..? Maybe I'll treat her to a titanium one ;)

Author:  greenstiles [ Tue Aug 07, 2012 8:50 am ]
Post subject: 

hi just moving the whole shock up /down the trunion will raise or lower back end...........no need for longer spring to do that. Plunger/push rod will still be same length so same travel of course. your better having a stock spring length that will go through i'ts proper compression than a longer spring with spare unusable travel i'm guessing, not 100% sure on that............perhaps if you are after a stiffer spring and a longer one but same pounds it may work the same??

but as i say you can higher/lower whole shock on trunion to alter angles

is judy sl and air fork ? if so a coil fork up front is best on these or a better quality air fork..........the rear end is so plush you see, think i ditched my air fork straight away as it held back the ride seriously. Nice pair of Psylo's or Fox coil forks would match very well or a modern good air fork.

Author:  Barneyballbags [ Tue Aug 07, 2012 9:05 am ]
Post subject: 

greenstiles wrote:
is judy sl and air fork ? if so a coil fork up front is best on these or a better quality air fork..........the rear end is so plush you see, think i ditched my air fork straight away as it held back the ride seriously. Nice pair of Psylo's or Fox coil forks would match very well or a modern good air fork.


They're Dukes, not Judys ;) - but I think they're air forks anyway. Here's the bike in all it's glory - this is a picture from the previous owner (the mudguards and various light mounts are going straight in the bin, and I've got a 90mm Thomson stem to swap for the Titec one):

Image

Author:  greenstiles [ Tue Aug 07, 2012 1:34 pm ]
Post subject: 

heres my old one,
Image

Author:  Barneyballbags [ Wed Aug 08, 2012 8:42 am ]
Post subject: 

greenstiles wrote:
heres my old one,
Image


The seat tube looks different, even though they look to be the same model/same year..?

My seat tube almost looks like 2 seperate pieces? Perhaps that's what Schwinn did on the smaller frames?

It arrives tomorrow :) :)

I've got Friday off :D :D :D

Author:  greenstiles [ Wed Aug 08, 2012 9:02 am ]
Post subject: 

yup your right ! to allow the seat post to go down on a small frame i guess.

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