T.R | Title | User | Personal Name | Date | Lines |
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1732.1 | The front is just one place where you can add gears | CIMNET::MJOHNSON | Matt Johnson, DTN 291-7856 | Fri Sep 07 1990 09:54 | 34 |
| With an 8-speed rear, running 39x24 doesn't mean you have to give
up close ratios. In Vermont (OK, it's not California, but...) I
often rode a 12-13-14-15-17-19-21-24 with a 39/53. That gives
you nearly a five-speed straight block in the upper gears. If
you switched to a 13-tooth outer cog, things would get even tighter
(13-14-15-16-17-19-21-24).
The inter-gear spacing on the 8-speed and 7-speeds might be the
same -- I haven't checked. But I think it would be hard to line
up the indexing, as the outer cog is offset 2mm due to the wider
axle. Go with friction mode when you use your 7's, if you go with
the 8.
Aesthetics aside, I still think you're looking for problems with
the "granny gear" setup. You've already seen the difficulty of
finding parts (like front derailleurs) that serve your purpose.
Getting a rear derailleur that 1) accepts lots of chain wrap,
but 2) is slanted for a tight gear cluster will be next to
impossible -- MAYBE Mt. Bike "racing" (short-cage) derailleurs
will do, but "short" for them is 13-24 vs. 13-34.
A final hot tip: I talked to Tom Craven, of Team 7-11, about
his gearing. He says that the 7-11 team DOES NOT use the new
"superglide" gears on its indexed 8 freehubs. Apparently,
superglide, while it lets you shift under power, compromises
shifting responsiveness by limiting the shift point to a single
position on the cluster. That means that you need a full wheel
rotation at times before the shift happens. At high speeds,
this is unnoticable, but apparently, during climbs, its annoying.
(I've never tried this myself, so I don't know....)
Good luck with your new rig,
MATT
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1732.2 | Racing-Triple feedback... | DELNI::MARCINKUS | | Fri Sep 07 1990 10:55 | 19 |
| Hey "Bat",
A "racing triple"??? Well, maybe, but I think you will be disappointed
with shifting performance. Even with Dura-Ace quality. I have
Dura-Ace on my two road bikes and I can feel a shifting difference
between the two. One bike has much longer chain stays and therefore a
longer chain. It's noticeable but on a training bike it's acceptable.
Such shifting performance on a racing bike just won't do it. I suggest
it would be too slow. So consider this; I also weigh in on the heavy
side, 178 or so. And I often ride very hilly terrain. I ride a 39x52
chainring setup and a 13-15-17-19-21-23-26, 7 speed freewheel. It
works great! At least for me. I can climb major hills and still find
a gear to keep pace with the fastest pack. In fact, this setup has
worked so well for me I run it on both my racing bike and sport bike.
Of course, be prepared to take some kiddin' on the "girly-man" gears
from your macho friends as I do. The payback will come when you ride by
them on a steep hill and have to wait at the top for them to catch up.
John
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1732.3 | still trying to sell myself | VERVE::BUCHANAN | Bat | Fri Sep 07 1990 20:10 | 74 |
| I'm still thinking this thing through. I've run this idea by a couple
good bike shops and they think it would work just fine. They've all
put triples on racing frames but usually with a large rear cluster.
My original setup was 42-52 x 13-26 7 speed. This does work OK and
gives a pretty low gear. However all the shifts are 2 or 3 teeth
jumps. If you've ever ridden a straight block you know how nice it
feels when each shift is only 1 tooth difference. You feel like you've
always got the perfect gear. I now am using a 39 inner ring with a
13-24 rear cluster. The rear is a bit closer but I really don't like
the jump from 39 to 53, it's just too big.
I should note that even 2 tooth jumps are better than what I've got
now. With the road bike out of action I put the TIME pedals and some
1.5" road times on the Mount Batbike and am trying to do battle with
the road bikes. I have a 6 speed 13-17-20-23-26-30. Pulling a 30 lb
mountain bike with big wheels up the hills is tough enough but my
biggest problem is finding the right gear. The jump from 13 to 17 is
huge!
My thinking is with the normal setup you have to make a choice, either
get close gearing and suffer on the hills or get low gears and live
with bigger gaps in the gearing. But why make the choice? Why not
have both? Keep the close rear cluster and get the lows by adding a
third chain ring.
As I said in an earlier note to change over an existing setup would
cost too much, but I'm thinking of building a new bike from scratch so
it wouldn't cost any more.
What will the shifting performance be like? That I'm not sure of. A
D-A derailluer can wrap 25 teeth, a short cage Deore XT 27, so all my
setups have been based on this limitation. So there will be no long
cage derailluers or 32 tooth rear cogs. I might also note that my
mountain bike setup shifts pretty damned good, the only time you really
notice it is when you drop from a large to smaller chain ring.
Just for comparison look at the gearing I was using vs. one possible
triple combination. The triple gives a higher high, a lower low and
more gears in my "sweet spot". By sweet spot I mean my most used range
which is from about 65 to 90"
39 53
13 ***** 110.08
14 75.21 102.21
15 70.20 95.40
17 61.94 84.18 needed wrap = 21
19 55.42 75.32
21 50.14 68.14
24 43.88 *****
40 50 60 70 80 90 100 110
56789012345678901234567890123456789012345678901234567890123456789012345678901234
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28 40 50
12 ***** 90.00 112.50
13 ***** 83.08 103.85
14 54.00 77.14 96.43
15 50.40 72.00 90.00 needed wrap = 26
16 47.25 67.50 84.38
18 42.00 60.00 75.00
20 37.80 54.00 *****
40 50 60 70 80 90 100 110
56789012345678901234567890123456789012345678901234567890123456789012345678901234
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1732.4 | Yeah... what he said. | GUIDUK::MONIN | | Fri Sep 07 1990 20:21 | 7 |
| I concur with the other warnings about poor performance on a triple.
When riding our tandem w/ Deore XT, I always have to factor in the
low-speed shifts compared with a Campy drive train on my road single.
Some of the loss is cable length, etc. but unfortunately, its the
middle-to-low ring shift (the one you really need when the road goes
vertical) that always seems unpredictable. Go w/ the eight instead,
or the big spread in front. I think you'll be lots happier
|
1732.5 | | JUMBLY::MACFADYEN | Send money now! | Mon Sep 10 1990 06:14 | 28 |
| > <<< Note 1732.1 by CIMNET::MJOHNSON "Matt Johnson, DTN 291-7856" >>>
>
> Apparently,
> superglide, while it lets you shift under power, compromises
> shifting responsiveness by limiting the shift point to a single
> position on the cluster. That means that you need a full wheel
> rotation at times before the shift happens. At high speeds,
> this is unnoticable, but apparently, during climbs, its annoying.
> (I've never tried this myself, so I don't know....)
I think yer man means Hyperglide (tm, reg) rather than Superglide (�).
Superglide is what Shimano calls their latest chainring shifting,
Hyperglide is for the cogs as the back. Anyway, I don't agree with him,
speaking as a recent convert to Hyperglide. On the bigger sprockets
there are at least two places on where the chain can be lifted onto the
sprocket for a downshift. I've never noticed a shifting delay -
Hyperglide is the fastest and most undramatic shifting I've ever used.
Then again I don't run a racing team and I'm not a pro.
Re chainwrap for the Batbike:
Why worry about the extremes of chainwrap when you can simply avoid
using them? I bet that adding a third chainring won't be a big deal.
Rod
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1732.6 | Racing triple sounds good to me! | BCSE::KLASMAN | ALL-IN-1 DESKtop for PCs. dtn 381-0731 | Mon Sep 10 1990 08:28 | 23 |
| I've thought about doing the same thing, living here in New Hampshire and having
a few steep hills in the area :^) I'm currently using 39x53, 13-21 7spd and am
pretty happy with it, except for the huge change when shifting the front. I
find I usually have to do a triple shift, 1 back, front, 1 back, to get the
right gear. Using SIS and Flight Controls on my Scott DH bars helps a lot, but
its still rather inconvenient. I'd never do this on a bike with shifters on the
down tube.
Non of the shops or other riders around here seem to thinks a racing triple is a
good idea, but I do. And I was surprised to read in Hinault's book that he
thought it might be a good idea, too.
My motivation for my current setup was the realization that although I had a 14-
spd bike, I really only used 6 speeds, with a 13-26, 42x53. But I just don't
want to be without bailout gears on the long, hilly rides.
My only suggestion would be to add the device that clamps on the seat tube to
prevent the chain from slipping off when sbifting to the granny ring. I put one
on our tandem and it really helps a lot. Don't remember what its called, but
its listed in the catalogs. I wish there was something that made the shift up
from the granny a little smoother.
Kevin
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1732.7 | | ALLVAX::JROTH | It's a bush recording... | Mon Sep 10 1990 08:41 | 7 |
| Marie Canins rode (and won) the TdF Femin on a road bike with a triple,
and she's certainly no wimp.
I've seen several people on Brevets with road bikes set up that way,
some of whom were pretty fast riders so the idea has merit.
- Jim
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1732.8 | The bat will soon be history | TPWEST::SHROYER | | Wed Sep 12 1990 12:04 | 7 |
| For those of you who didn't know, the bat's group is being
disbanded (they don't offer the package in the silicon valley) and the
bat will soon be gainfully employed in a non-dec environment. He
resigned Monday. I hope he will still be available for our lunch
rides all winter.
Should we get his digital jersey before he leaves?
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1732.9 | Taking it personally? | CIMNET::MJOHNSON | Matt Johnson, DTN 291-7856 | Wed Sep 12 1990 12:30 | 4 |
| Gosh, I didn't mean to be that negative about the racing triple
idea!
MATT
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1732.10 | still thinking | VERVE::BUCHANAN | Bat | Wed Sep 12 1990 13:39 | 9 |
|
> Gosh, I didn't mean to be that negative about the racing triple
> idea!
> MATT
When interviewing with companies I made it a point to ask their opinion on the
racing triple idea. If they laughed, I walked!
|