42 chainring versus 39. Material Difference?

[Delpo]

I have an upcoming race that has several 3K segments that are "false flats". The peloton will be cruising at 18/20 mph on these segments and in scouting the route I have not been able to hold the pace in the 53. At the same time I have to spin the hell out of the 39 to keep up. Will a 42 chainring provide a material difference to the 39 and at the same time provide relief from the 53? Looking forward to input.

Delpo

[musgravecycles]

Yes!

I lived in MI for the last 7 years, I wouldn't have traded my beloved 42 (44 in the summer) for anything. The difference between a 39 and a 42 is astounding...

[Sandy]

What size cassette, please.



Sandy

[Delpo]

What size cassette, please.



Sandy

Sandy, I move between a 11/23 and a 12/25 10 speed. For this race I did the scouting on the 12/25.

Delpo

[L84dinr]

FWIW when i started riding again a couple of years back I was riding my old six speed freewheel with 53/42 combo up front. Then purchased a basso with eight speed and a 39/52 combo. I noticed a big difference between the 39 and the 42. I like the 39 in the early part of the season... and the middle part, and the end... ;>)

[shinomaster]

When I was younger I rode a 42 (with a 12-21 in the back) all around Boston...I loved it. I didn't need the big ring very often as you can go pretty fast in a 42....
I took it off as soon as I moved to Portland.

[dauwhe]

My big ring is a 44!

Dave

[Xyzzy]

My big ring is a 44!
Mine is too. I just never use the 53. (Well, I do sometimes, to make sure it still works.)

There are three things I like about the 44. One, when you do shift to the 53, it is lightning quick. Second, it looks bad äss. Three, with the proper cassette and the right conditions, it is the perfect gearing for where I live. (Which is moderately rolling hills that are far from mountainous. No more than 5 minutes for any climb, and that's if you are having a bad day.)

They say EM was a big fan of the 44 for climbing. I figure he probably had a 12/13-19/21 cluster. Of course, we aren't EM. A 14-23 in the back makes for a lot of fun with a 44. (A Record 14-23 cassette would complete my life.)

http://www.mersenneforum.org/images/smilies/extra/blahblah.gif


http://forums.thepaceline.net/attachment.php?attachmentid=21444&stc=1

[sw3759]

for flat to rolling hills a 42/53 w/12-23 is so much nicer than a 39/53..and good for about 30mph without cross chaining.unless you have lots of long sustained climbs i bet you will be much happier with the 42.also,better front shifting is a bonus atmo.


Scott

[Tom]

I'm running a Campy 39-53 with their 11-25 in the back. It's a good compromise, the 39-12 is a little off line but it's nice to get up to about 24mph in the little ring. I'm not sure if that would do the trick in your race conditions but for me it's good because there are days I am not supposed to be committing to any kind of effort so I tell myself "No front shifts today" and leave it in the little ring.

[cs124]

Another vote for the 42 for flat-to-rolling terrain...but...I'd be very surprised if you find yourself racing up that climb in the small ring. Don't underestimate the power of adrenaline (and the draft!).

[Climb01742]

42 is very nice over flat to rolling terrain. you will notice it on good size climbs. a 42 is very good for training, vs riding.

[Dave]

The difference between using a 42 instead of a 39 is the same as using one cog smaller. In other words, a 42/15 is about the same a 39/14.

I don't understand the problem with going 18-20 mph in the little ring. That's only 90 rpm in the 13-15 tooth range.

Sounds like a cadence problem to me.

[david]

dating myself here, but when i was a wee lad (early twenties) everybody rode 42x52 upfront with a 13/21 six speed in the back.
this was in norcal, berkeley.
we'd put on a 23 for the really hilly races.
but mostly 42x21 for the norcal hills.
we used to stand while climbing more than folks do today.
quienes mach macho?

[chuckred]

dating myself here, but when i was a wee lad (early twenties) everybody rode 42x52 upfront with a 13/21 six speed in the back.
this was in norcal, berkeley.
we'd put on a 23 for the really hilly races.
but mostly 42x21 for the norcal hills.
we used to stand while climbing more than folks do today.
quienes mach macho?

I've still got my 13/21 five speed on my bike onthe trainer... guess I'm a couple years older...

[david]

I've still got my 13/21 five speed on my bike onthe trainer... guess I'm a couple years older...

and definitely more macho. :)

[Ti Designs]

The difference between using a 42 instead of a 39 is the same as using one cog smaller. In other words, a 42/15 is about the same a 39/14.


It's a chainline thing. They may very well be just about the same gear, but with a 39x53 and 12-X your chain is starting to hit the side of the large ring. By comparison, the 42x53 has a bit more swing before hitting the chainring, and one extra gear position on back.

John Allis has always run a 44x52 which he likes because the 44 keeps him in that good range on the back (no cadence problem with John). I started running a 44x55 this year (they were given to me for free - everybody else is looking for compact 10, who wants huge 9-speed???). I love the 44. On spirited group rides I find I can just stay in the small ring. The 55 is a bit large but it's more of a statement than a usable bike part...

[vaxn8r]

It's a chainline thing. They may very well be just about the same gear, but with a 39x53 and 12-X your chain is starting to hit the side of the large ring. By comparison, the 42x53 has a bit more swing before hitting the chainring, and one extra gear position on back.

John Allis has always run a 44x52 which he likes because the 44 keeps him in that good range on the back (no cadence problem with John). I started running a 44x55 this year (they were given to me for free - everybody else is looking for compact 10, who wants huge 9-speed???). I love the 44. On spirited group rides I find I can just stay in the small ring. The 55 is a bit large but it's more of a statement than a usable bike part...
Well, in a pinch you ought to be able to easily use a 53x23 on a 12-25 cassette. I wouldn't recommend it all the time but for the specific application I don't see why this shouldn't work. As I think about it though, if you're in a 53x23 you probably wont be going 18-20 mph anyway. Maybe this isn't a gearing issue but more a strength issue.

[Dave]

It's a chainline thing. They may very well be just about the same gear, but with a 39x53 and 12-X your chain is starting to hit the side of the large ring. By comparison, the 42x53 has a bit more swing before hitting the chainring, and one extra gear position on back.

John Allis has always run a 44x52 which he likes because the 44 keeps him in that good range on the back (no cadence problem with John). I started running a 44x55 this year (they were given to me for free - everybody else is looking for compact 10, who wants huge 9-speed???). I love the 44. On spirited group rides I find I can just stay in the small ring. The 55 is a bit large but it's more of a statement than a usable bike part...

A 39/13 at 100 rpm will produce over 23 mph, well above the 18-20 mph mentioned in the OP. To do that speed, all you need is a 39/15, so chainline is NOT the issue at that speed.

[Ti Designs]

A 39/13 at 100 rpm will produce over 23 mph, well above the 18-20 mph mentioned in the OP. To do that speed, all you need is a 39/15, so chainline is NOT the issue at that speed.

Average speed isn't part of the real world...

[Dave]

Average speed isn't part of the real world...


The OP mentioned a speed RANGE of 18-20. Nothing about average. A rider who can't go 23-24 mph with a 39/14 can't spin. Unless the chainstays are really short on the OP's bike he should be able to use the 39/13 and get up to 26 mph. Still seems like a cadence problem

[Climb01742]

The 55 is a bit large but it's more of a statement than a usable bike part...

ed, you're one of a kind.

[RPS]

I recommend you look at it a little differently. Regardless of how fast you are going or how fast your optimum cadence is, there is a point (relative to center of cassette) at which small ring to small cog is essentially the same ratio as large ring to large cog. Knowing the chainline in either direction at this equivalent crossover gearing and making sure that it’s adequate is what’s important IMO so that you have every possibility covered.

Running 53/39 and 53/42 rings with your two cassette options (11-23 and 12-25) on a spreadsheet reveals that you should never have to be more than on the third cog from either end of the cassette.

The tightest gearing option IMO would be 53/42 with 12-25, which has the crossover at 42/15 and 53/19. In both cases you are on the fourth cog from either end of the cassette -- lots of options there.

[Grant McLean]

I think that as long as you are aware of the cross chain issue,
you can happily choose whatever chainring combinations work
for you personally.

It was the mid 90's, with the switch to 9sp, when I recall that
stock bikes started coming with 39/53 as the standard set up,
insead of 42/52 or 42/53.

Since it's not that hilly around here, I find that some people
who starting riding before 39's were common just stayed with their
42 tooth preference, while others have experimented with compact.

It's a funny thing about change. Sometimes when you find something
that works, there is a reluctance to change! I sure notice a lot of
newbies riding triples in the 32/12 combo though...

g
(mr.42)

[regularguy412]

The tightest gearing option IMO would be 53/42 with 12-25, which has the crossover at 42/15 and 53/19. In both cases you are on the fourth cog from either end of the cassette -- lots of options there.
<snipped>

This is basically what I run, except in 8-speed (12-21). I find I use the 15 and the 16 with both rings, quite often. There is minimal unnecessary shifting. If things get really hilly, I put on the 39 and change the cassette to 13-24.

Mike in AR

[Ti Designs]

The OP mentioned a speed RANGE of 18-20. Nothing about average. A rider who can't go 23-24 mph with a 39/14 can't spin. Unless the chainstays are really short on the OP's bike he should be able to use the 39/13 and get up to 26 mph. Still seems like a cadence problem

A speed range of 18-20 on a group ride? When I was about 4 I figured out that Santa Clause doesn't really fly around on a sleigh. Somewhere in my mid 20's I figured out that the tooth fairy doesn't exist. Now you expect me to belive that a group of riders is going to hold a speed range of 18-20 mph?

I spend 6 months a year on a fixed gear riding with groups, most if not all of them are on geared bikes. I know all too well that sometimes I'm crusing along at 75 RPM, other times I'm at 175 RPM's wondering if my legs are going to fly off before my lungs explode. I would gladly pay someone to enforce a speed range on some of those rides.

As for gearing and chainrings, I've never taken out a calculator and figured out the gear inches or crossover was. I figure I have 5 usable gears in each chainring, the large cog in the back is the bail out gear, the small one back there is just in case I ride off a cliff and feel the need to pedal on the way down. That leaves a total of 8 usable gears, 'cept I have that 55, so it's more like 4 usable gears and a whole lot of intimidation. If you only have 4 usable gears you know pretty quickly if they're the right ones. I don't turn a 39...

[Dave]

A speed range of 18-20 on a group ride? When I was about 4 I figured out that Santa Clause doesn't really fly around on a sleigh. Somewhere in my mid 20's I figured out that the tooth fairy doesn't exist. Now you expect me to belive that a group of riders is going to hold a speed range of 18-20 mph?



Maybe you should reread the OP. The question was regarding a SINGLE stretch of road in a RACE, where an speed of 18-20 was anticipated. Here's the quote:

"I have an upcoming race that has several 3K segments that are "false flats". The peloton will be cruising at 18/20 mph on these segments and in scouting the route I have not been able to hold the pace in the 53. At the same time I have to spin the hell out of the 39 to keep up. Will a 42 chainring provide a material difference to the 39 and at the same time provide relief from the 53? Looking forward to input."

I've got no clue how the OP came up with this, but IMO, you should be able to ride anywhere from 10-24 mph in the little ring. I think what's being suggested is that the speed range will require contant shifting back and forth between the rings. If not, I don't know what the OP's asking. For the matter, I wonder how he knows which way and how strong the wind will be blowing on the day of the race. That alone will could alter the speed and choice of chainring.

I find your comments interesting, but why not stick to the original question rather than some tangent?

[Matt Barkley]

I dig the 42 though currently run the standard 39/53 with an 11/23 or 12/23 in the back.

52/42 is what I started out on and learned to spin with the 42 and could stay in it much longer and not cross chain as much. With a 39 I definitely do better having the 11 which gains me a little on the cross-chaining in that 39... Really dig cranking over the top of climbs in the 42 or 44 than the 39 - but that 39 may be what got you up the climb.

Been thinking about this stuff and had a BostonDrunk revelation the other night... 52/42 with the 11/25... 52x11 is plenty big and 42x25 plenty small for my riding style. I have yet to try this out.... :beer: - Matt

[Ti Designs]

I find your comments interesting, but why not stick to the original question rather than some tangent?

'cause I don't know where these "false flats" are??? The tangent has to do with real life on the bike, the OP has to do with very specific conditions that I'm not going to be subjected to. My alternate answer is to spin the 39 where you can and hold onto the seatpost of the guy next to you when it gets to fast.

[stevep]

I have an upcoming race that has several 3K segments that are "false flats". The peloton will be cruising at 18/20 mph on these segments and in scouting the route I have not been able to hold the pace in the 53. At the same time I have to spin the hell out of the 39 to keep up. Will a 42 chainring provide a material difference to the 39 and at the same time provide relief from the 53? Looking forward to input.

Delpo

in the actual race you will have no trouble using the 53- something.
fahgettaboutit.