Community Forums

Mike8253 · 01-20-2018, 09:05 AM

This rear springs subject came up on an earlier thread where it was determined that the only difference between the 24K and 26K chassis is the spring rate of the rear leaf spring sets, with the 26K a chassis having the higher deflection rating. I happen to have a 2016 Tiffin Allegro 34PA delivered on the 24K chassis. In that model year you had to specify the chassis and I didn't know. My fault, I didn't know. Today this model is delivered only on the 26K chassis. So I have the 24K chassis, and I have had it weighed on all four corners at travel loading we are good on all combinations of weights as well as on each corner. So today there's no concerns. Also, my toad is only 3700 lbs. But for the future, there's always the possibility I will want to carry more stuff, and so was thinking about whether there is a reasonable means to put in the higher rated springs to get the added 2000 lbs. of capability. And I could do this without compromising my 30K CGWR because of my toad's weight. Does anyone have experience with rear springs replacement on the F53? Pipe dream as a mod because it's going to be more complicated and costly than I am thinking. Or is it a capability improvement I should pursue? Thanks in advance for your inputs. I am just in early data gathering mode at this point.

Scarab0088 · 01-20-2018, 01:05 PM

I cannot address/corroborate the 24K v 26K differences in the F53...but;

Why bother with the springs?

High quality overload air bags are affordable and easy to add to these chassis.
The benefit to air bags is the tune-ability of the supplimental suspension. If you want the higher capacity...pump the air bag up. If you want a more compliant ride...release some air in the bags.
Like: https://www.ultrarvproducts.com/5734...F53-(2009-2016)

Just be very sure to never exceed the gross axle weight capacity. The axle could most surely carry overweight, but it will usually increase heat and reduce bearing life.

About the 30K Gross Combined Weight Rating...this number does not change with suspension upgrades. GCWR is the amount of total rolling weight (RV and towed load) that can be safely moved by the RV's drive-line. Changing GCWR requires changes in the engine-transmission-axle set-up...usually supplimental cooling and an engine tuner is the first steps owners take in this area.

Best luck

Mike8253 · 01-20-2018, 04:26 PM

Quote:

Originally Posted by Scarab0088

I cannot address/corroborate the 24K v 26K differences in the F53...but;

Why bother with the springs?

High quality overload air bags are affordable and easy to add to these chassis.
The benefit to air bags is the tune-ability of the supplimental suspension. If you want the higher capacity...pump the air bag up. If you want a more compliant ride...release some air in the bags.
Like: https://www.ultrarvproducts.com/5734...F53-(2009-2016)

Just be very sure to never exceed the gross axle weight capacity. The axle could most surely carry overweight, but it will usually increase heat and reduce bearing life.

About the 30K Gross Combined Weight Rating...this number does not change with suspension upgrades. GCWR is the amount of total rolling weight (RV and towed load) that can be safely moved by the RV's drive-line. Changing GCWR requires changes in the engine-transmission-axle set-up...usually supplimental cooling and an engine tuner is the first steps owners take in this area.

Best luck

Thanks for your response. Just to clarify, the 24K and 26K chassis are identical save the rear springs, and the engine/transmission, power management, and all other chassis systems do not change between the two weight ratings. I'm not looking to redesign it as I am very happy with how it drives and rides, I'm just trying to find out if the rear spring changeout is a straight forward and cost effective way to use all the capability already resident in the existing chassis system. What I really don't know is how complicated is it to remove the springs from a fully assembled motorhome.

time2run · 01-20-2018, 05:33 PM

Quote:

Originally Posted by Mike8253

This rear springs subject came up on an earlier thread where it was determined that the only difference between the 24K and 26K chassis is the spring rate of the rear leaf spring sets, with the 26K a chassis having the higher deflection rating. I happen to have a 2016 Tiffin Allegro 34PA delivered on the 24K chassis. In that model year you had to specify the chassis and I didn't know. My fault, I didn't know. Today this model is delivered only on the 26K chassis. So I have the 24K chassis, and I have had it weighed on all four corners at travel loading we are good on all combinations of weights as well as on each corner. So today there's no concerns. Also, my toad is only 3700 lbs. But for the future, there's always the possibility I will want to carry more stuff, and so was thinking about whether there is a reasonable means to put in the higher rated springs to get the added 2000 lbs. of capability. And I could do this without compromising my 30K CGWR because of my toad's weight. Does anyone have experience with rear springs replacement on the F53? Pipe dream as a mod because it's going to be more complicated and costly than I am thinking. Or is it a capability improvement I should pursue? Thanks in advance for your inputs. I am just in early data gathering mode at this point.

I have a 2018 34PA on the 24K chassis which is still the stock size. You have to request the 26K chassis as a $3K add. I made the mistake of believing the Tiffin website information and did not realize there was a difference.

For what it’s worth, I would suggest anybody ordering the Allegro should opt for the 26K chassis. I have very little OCCC on the 24K chassis.

Mike8253 · 01-20-2018, 06:47 PM

Thanks for your reply, but I believe you should really post this as it's own topic on the Tiffin forum to have the greatest readership and impact.

time2run · 01-21-2018, 02:09 PM

Quote:

Originally Posted by Mike8253

Thanks for your reply, but I believe you should really post this as it's own topic on the Tiffin forum to have the greatest readership and impact.

Thanks and most probably will. The major point was to clarify that the 34PA still comes standard with the 24K frame with the 26K as a cost added option.

Cheers

Mike8253 · 01-21-2018, 02:12 PM

So if you could upgrade the rear springs at a reasonable cost for the added 2000 lbs. capability, would you?

time2run · 01-21-2018, 04:55 PM

Quote:

Originally Posted by Mike8253

So if you could upgrade the rear springs at a reasonable cost for the added 2000 lbs. capability, would you?

Mike-

Absolutely. I wish I would have known the difference during the ordering process and I would have ordered it with the larger frame, extra cost and all. I figure the 26K frame should have given me another 1500 pounds of carrying capacity. As it is now, after you add me, my wife and about 20 gallons of travel fresh water, we have about 800 pounds max for all other cargo. Boondocking is totally out of the question as the extra weight would easily put me over the limit.

I have my 34PA at the dealer now and they are supposed to find out if the upgrade is feasible. I’ll let you know what I find out. Shouldn’t be too much difference between our two F53 chassis’s.

Mike8253 · 01-21-2018, 05:37 PM

I will be very anxious to hear. Thanks.

Scarab0088 · 01-22-2018, 12:22 AM

Are you all saying the 24K and 26K only differ in the rear spring pack?

Quote:

Originally Posted by time2run

I’ve noticed on a couple of posts where it was stated that the 34PA now comes standard with the 26K frame. Well I found out the hard way that it does not and the standard frame is still the 24K. The 26K frame is a $3K option add.

If you look at Tiffin’s website and at the 34PA specs, it will say 26K on one form and 24K on another form. Very confusing. I would suggest anybody buying a F53 chassis ask which frame sizes are available.

The OCCC for the 24K is only 1200 pounds for cargo and passengers. Fresh water is considered cargo using the OCCC methodology.

http://www.irv2.com/forums/f106/34pa...ze-375827.html

I would bet that the spring hangers are not identical...but have no specifics.

BTW: Regardless of frame, overload airbags would still be better to supplement a spring suspension over heavier springs...soft or stiff as you select for the airbag pressure. That's why DP's use airbags

Sweetbriar · 01-22-2018, 05:14 AM

Before you get too deep into the idea physically verify the rear axle model. Get under the coach and find the tag on the front of the differential housing which will list the model number. If it's anything other than a 17060S then the axle is not the 17,500 weight rated model needed for the 26,000 GVWR chassis and probably a S130 15,000 Lbs model.

Mike8253 · 01-22-2018, 06:13 AM

As I read the Ford F53 chassis spec sheet, that axle is the one used for both the 24K and 26K weight ratings.

Mike8253 · 01-22-2018, 06:48 AM

Quote:

Originally Posted by Scarab0088

Are you all saying the 24K and 26K only differ in the rear spring pack?

http://www.irv2.com/forums/f106/34pa...ze-375827.html

I would bet that the spring hangers are not identical...but have no specifics.

BTW: Regardless of frame, overload airbags would still be better to supplement a spring suspension over heavier springs...soft or stiff as you select for the airbag pressure. That's why DP's use airbags

That's correct.

Sweetbriar · 01-22-2018, 02:16 PM

I would not trust a spec sheet until verified. Production could change at anytime while the spec sheet is updated once a model year. The same for the model year chassis the coach is built on. The coach could be a 2016 while the chassis could be a 2015. Chassis and coach model years are not always in sync.